Determining a suitability of network nodes for rf-based presence and/or location detection

ABSTRACT

A system ( 1 ) for selecting one or more devices in a wireless network for transmitting, receiving and/or processing a radio frequency signal for presence and/or location detection comprises at least one processor ( 5 ) configured to determine a suitability of each of a plurality of devices ( 11 - 15 ) for transmitting, receiving and/or processing a radio frequency signal for presence and/or location detection, select a subset of devices from the 5 plurality of devices based on the suitability determined for each of the plurality of devices, and instruct at least one of the subset of devices to act as a device for transmitting, receiving and/or processing a radio frequency signal for presence and/or location detection.

FIELD OF THE INVENTION

The invention relates to a system, a method and a computer program forRF-based presence detection and/or localization.

In particular, the invention relates to a system for selecting one ormore devices in a wireless network for transmitting, receiving and/orprocessing a radio frequency signal for presence and/or locationdetection, a method of selecting one or more devices in a wirelessnetwork for transmitting, receiving and/or processing a radio frequencysignal for presence and/or location detection and a computer programproduct enabling a computer system to perform such a method.

BACKGROUND OF THE INVENTION

RF-based presence detection is a promising technology that may replaceor enhance PIR-based presence detection. RF-based localization allowsdevices to be located indoors. RF-based presence detection is disclosedin US 2017/0359804 A1, for example.

US 2017/0359804 A1 discloses a first wireless network devicecommunicating wireless network traffic on a first subset of wirelesscommunication channels in a wireless network. The first wireless networkdevice receives motion detection signals transmitted through a space bya second wireless network device. The motion detection signals arereceived on a second subset of wireless communication channels. Themotion detection signals are processed to detect motion of an object inthe space.

Typically, all devices capable of performing RF-based presence detectionand/or localization would be configured to help perform this RF-basedpresence detection and/or localization in the system of US 2017/0359804A1. However, performing this task reduces a device's capacity tocommunicate wireless network traffic and configuring all capable devicesto perform RF-based presence detection and/or localization might not beoptimal use of resources in certain applications.

US20100178929A1 discloses a system and method in a wirelesscommunication system having plural base stations and a MSC with anetwork overlay geo-location system.

US20170132909A1 discloses a system which are provided for securitysystem re-arming. Input invoking restricted credentials may be received.The security system of an environment may be changed from a first modeto a second mode based on the restricted credentials. The restrictedcredentials used to change the security system to the second mode may bedetermined to be near expiration based on an expiration condition of therestricted credentials. A notification may be sent to a personassociated with the restricted credentials including a reminder to usethe restricted credentials to change the security system to the firstmode before the restricted credentials expire.

SUMMARY OF THE INVENTION

It is a first object of the invention to provide a system, which is ableto configure a wireless network to perform RF-based presence detectionand/or localization while leaving sufficient resources, e.g. bandwidth,for network communication.

It is a second object of the invention to provide a method, which isable to configure a wireless network to perform RF-based presencedetection and/or localization while leaving sufficient resources, e.g.bandwidth, for network communication.

In a first aspect, the system for selecting one or more devices in awireless network for transmitting, receiving and/or processing a radiofrequency signal for presence and/or location detection comprises atleast one processor configured to determine a suitability of each of aplurality of devices for transmitting, receiving and/or processing aradio frequency signal for presence and/or location detection, select asubset of devices from said plurality of devices based on saidsuitability determined for each of said plurality of devices, andinstruct at least one of said subset of devices to act as a device fortransmitting, receiving and/or processing a radio frequency signal forpresence and/or location detection. This system is also referred to as“controller” or “orchestrator”.

The inventors have recognized that in certain situations not all devicesin a wireless network should transmit, receive and/or process a radiofrequency signal for presence and/or location detection, but that it isbeneficial to select a subset of devices based on their suitability forthis function in these situations. By not selecting devices that are notsuitable or are less suitable, these devices have more time for networkcommunication and resources for network communication are thus notwasted. RF-based presence detection is also referred to as RF-basedsensing and RF-based localization (location detection) is also referredto as RF-based asset tracking. Thus, more suitable devices are preferredover less suitable or non-suitable devices.

Said plurality of devices may comprise at least one light device. Lightdevices are more and more equipped with wireless transceivers to enablesmart functionality and are often located in quantities and at locationswell suited for RF-based presence and/or location detectionapplications. Presence detection may be used to perform people countingor people tracking, for example. If a user is detected to be present, aposture or a movement of his body may be determined. The term RF-basedpresence detection covers any RF-based sensing application. Locationdetection may be used to perform gesture detection, for example. Theterm RF-based location detection covers any RF-based trackingapplication. The network may be mesh network or a star network, forexample. For instance, in a star configuration, a gateway may connectwith a single hop to all lights in the room. In this case, one or moreof the lights may be selected for RF-based sensing.

Said at least one processor may be configured to determine at least partof said suitability of a device of said plurality of devices byassessing expected and/or past use of a lighting function and/or networkfunction of said device and/or any other expected and/or past use ofsaid device. For example, a light that is always on may be preferable toa light of which the on/off state changes often. The expected use of alighting function may be derived from a floorplan or from other devicesin similar situations (e.g. from devices on a floor in the same buildingon which wireless lighting has already been installed).

When assessing the use of a network function, how this use is performedmay also be assessed. For example, a node that is used a lot to routemessages between two other nodes and succeeds 100% of the times inrelaying the message does not perform the same as a node that does thesame routing, but succeeds only 70%. The latter could be an indicationof some external factor affecting the node's operation (regardless ofthe level of usage). The performance of a network function such asrouting messages and being a proxy node for streaming could possiblyalso result in visible impact (though not necessarily on the deviceitself, but rather on nodes served by it) and this use of the device maybe assessed as well.

Said at least one device may use a first protocol to transmit, receiveand/or process a radio frequency signal and a second protocol to receivenetwork messages. For example, network messages may be received usingthe Zigbee protocol or the Thread protocol and RF based presence and/orlocation detection may performed using Bluetooth signals. Alternatively,said at least one device may use the same protocol, e.g. Zigbee, totransmit, receive and/or process a radio frequency signal and receivenetwork messages.

Said least one processor may be configured to determine at least part ofsaid suitability of a device of said plurality of devices by assessingat least one of: said device's hardware and software capabilities, saiddevice's RF characteristics, said device's mounting orientation,wireless interference close to said device, and whether said device isoperated by a battery-operated wall switch, a legacy wall switch, anoccupancy sensor, a motion sensor, a vacancy sensor, a window blindcontroller, a sensor bundle and/or a mains-powered wireless-switch. SaidRF characteristics may comprise radiation patterns, directionality ofthe antenna, transmit power, and/or reception sensitivity, for example.Said sensor bundle may comprise a CO2 sensor, a humidity sensor, amicrophone (for sound analytics), a volatile organic component sensorand/or a temperature sensor, for example. Sensors that use Ultra WideBand (UWB) and LiFi sensor technologies may also be used.

A light controlled by a legacy wall switch may be considered to be lesssuitable, because the light switch cuts the power to the light, therebymaking it incapable to perform RF-based sensing. If a light iscontrolled by an occupancy sensor, it may be considered to be lesssuitable for RF-based sensing, as the latency to respond to a change ofoccupancy might be worsened. If a light is equipped with a sensor bundlebut the sensor bundle output is not used for the purpose of real-timeadjustments of the light output of other lighting devices (e.g. certainwireless lights map the temperature and humidity across the room withoutany dynamic lighting control e.g. an emergency lighting fixture) and/ornot used for real time adjustment of this lighting device hosting thesensor bundle, the latency will typically not be critical.

Said at least one processor may be configured to select said subset ofdevices as part of commissioning said plurality of devices and/or aftercommissioning said plurality of devices. Said subset of devices may beselected after use of said plurality of devices or after receivinginformation from a similar building space elsewhere (e.g. from anotherfloor or another building). In the commissioning process, some devicesmay be marked as being more or less suitable for the sending functionthan others. A suitability of a device may be determined, for instance,based on how critical the device is for routing messages. The latter isan indication of how much additional resources/bandwidth the devicewould have left for additional RF-based sensing. A suitability of adevice may alternatively or additionally be determined, for instance,based on how much non-routing or non-rebroadcasting traffic a deviceneeds to send (sensor) or receive (actuator, e.g. light), as theassociated latency requirement may influence the decision onsuitability.

Said at least one processor may be configured to determine saidsuitability of each of said plurality of devices for transmitting,receiving and/or processing said radio frequency signal by determining asuitability of a plurality of groups of said plurality of devices fortransmitting, receiving and/or processing said radio frequency signal.Each group comprises at least two of said plurality of devices and willnormally comprise a first device for transmitting the RF signal and oneor more second devices for receiving the RF signal. It may beadvantageous to select as first device a device which can be heard by asmany other devices in the vicinity as possible. If this device can beheard by a plurality of other devices, this device may be included asfirst device in a plurality of groups over another device which is heardby fewer nodes. Thereby, many devices can determine the RSSI based onthe same single signal sent by the first device. For instance, in acommercial office setting, messages of a light close to a normally openfirewall door interconnecting two office sub-spaces may be heard by manymore lights in both subspaces as another light in vicinity of thefirewall but farther away. It may be advantageous to select as seconddevice a device which can hear as many other devices in the vicinity aspossible. The groups may be pairs, for example.

Said least one processor may be configured to determine whether twogroups of said plurality of devices have a device in common and target asame or adjacent sensing area and determine one of said two groups notto be suitable in dependence on said determination. This may bebeneficial if the device in common is the second device, i.e. the devicereceiving the RF signal, in at least one of the two groups, or if thedevice in common is the first device, i.e. the device transmitting theRF signal, in both groups and it is not possible to transmit a single RFsignal to both receiving devices. If the two groups have the sametransmitting device in common and the receiving devices are able toreceive and process the same RF signal from this transmitting device,then this may have advantages when it comes to efficient use of thewireless spectrum. The groups may be pairs, for example.

Said least one processor may be configured to determine whether acommunication quality between a pair of said plurality of devices isbelow a certain threshold and determine said pair not to be suitable independence on said determination.

Said least one processor may be configured to determine, at a latermoment, a further suitability of each of said plurality of devices fortransmitting, receiving and/or processing said radio frequency signal,select a further subset of devices from said plurality of devices basedon said further suitability determined for each of said plurality ofdevices, and instruct at least one of said further subset of devices toact as a device for transmitting, receiving and/or processing a radiofrequency signal for presence and/or location detection. By determiningthe suitability repeatedly, changes in the devices or in the environmentmay be taken into account. For instance, a piece of office furniture maybe shifted, worsening the detection performance of the originaldetection pair of lights, a device may be regularly depowered, or adevice may suffer interference from a nearby WiFi access point duringoffice hours (which likely won't be detected at the time of installationin a building since at that moment WiFi might not yet be installed andcertainly not heavily used by the employees).

The further suitability of a device may depend on its current role inthe network. For example, if a device has one or more Zigbee end-device(ZED) children, if a device is routing on behalf of other nodes, or if adevice is proxying for a Zigbee Green Power Device (GPD) (especially ifthere are only few selected proxies), then it is beneficial not toswitch this device from a Zigbee routing role to a Zigbee end-devicerole. If a luminaire comprises multiple Zigbee devices, then one ofthese devices may have a role as Zigbee end-device and the other mayhave a role as Zigbee router. The former device could then be selectedfor transmitting, receiving and/or processing the radio frequencysignal.

Said at least one processor may be configured to determine at least partof said suitability of a device of said plurality of devices based onhistorical data relating to said device and/or by assessing saiddevice's spatial location and/or environmental condition. As an exampleof the latter, if RF-based sensing is performed by garden lighting, aluminaire in the sun might have different sensitivity than a luminairein the shade, e.g. due to expansion of substrates which lead tovariations in a track antenna's length and thermal shift of componentvalues like RF matching circuits and crystals, which lead to a deviatedcarrier frequency with respect to the center frequency of the selectedband, for example. Said environmental condition may be a weathercondition, for example.

Said at least one processor may be configured to determine atransmission power and/or directionality for a radio frequency signal tobe transmitted by said device based on said device's spatial location.

Said at least one processor may be configured to determine saidsuitability of each of said plurality of devices for transmitting,receiving and/or processing said radio frequency sensing signal for acertain type of detection.

Said at least one processor may be configured to determine at least partof said suitability of a device of said plurality of devices based on anamount of time available to said device for transmitting or receivingsaid radio frequency signal.

In a second aspect, the method of selecting one or more devices in awireless network for transmitting, receiving and/or processing a radiofrequency signal for presence and/or location detection comprisesdetermining a suitability of each of a plurality of devices fortransmitting, receiving and/or processing a radio frequency signal forpresence and/or location detection, selecting a subset of devices fromsaid plurality of devices based on said suitability determined for eachof said plurality of devices, and instructing at least one of saidsubset of devices to act as a device for transmitting, receiving and/orprocessing a radio frequency signal for presence and/or locationdetection. Said method may be performed by software running on aprogrammable device. This software may be provided as a computer programproduct.

Moreover, a computer program for carrying out the methods describedherein, as well as a non-transitory computer readable storage-mediumstoring the computer program are provided. A computer program may, forexample, be downloaded by or uploaded to an existing device or be storedupon manufacturing of these systems.

A non-transitory computer-readable storage medium stores at least asoftware code portion, the software code portion, when executed orprocessed by a computer, being configured to perform executableoperations comprising: determining a suitability of each of a pluralityof devices for transmitting, receiving and/or processing a radiofrequency signal for presence and/or location detection, selecting asubset of devices from said plurality of devices based on saidsuitability determined for each of said plurality of devices, andinstructing at least one of said subset of devices to act as a devicefor transmitting, receiving and/or processing a radio frequency signalfor presence and/or location detection.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a device, a method or a computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit”, “module” or “system.”Functions described in this disclosure may be implemented as analgorithm executed by a processor/microprocessor of a computer.Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied, e.g., stored,thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples of a computer readable storage medium may include, butare not limited to, the following: an electrical connection having oneor more wires, a portable computer diskette, a hard disk, a randomaccess memory (RAM), a read-only memory (ROM), an erasable programmableread-only memory (EPROM or Flash memory), an optical fiber, a portablecompact disc read-only memory (CD-ROM), an optical storage device, amagnetic storage device, or any suitable combination of the foregoing.In the context of the present invention, a computer readable storagemedium may be any tangible medium that can contain, or store, a programfor use by or in connection with an instruction execution system,apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber, cable, RF, etc., or any suitable combination ofthe foregoing. Computer program code for carrying out operations foraspects of the present invention may be written in any combination ofone or more programming languages, including an object orientedprogramming language such as Java™, Smalltalk, C++ or the like,conventional procedural programming languages, such as the “C”programming language or similar programming languages, and functionalprogramming languages such as Scala, Haskell or the like. The programcode may execute entirely on the user's computer, partly on the user'scomputer, as a stand-alone software package, partly on the user'scomputer and partly on a remote computer, or entirely on the remotecomputer or server. In the latter scenario, the remote computer may beconnected to the user's computer through any type of network, includinga local area network (LAN) or a wide area network (WAN), or theconnection may be made to an external computer (for example, through theInternet using an Internet Service Provider).

Aspects of the present invention are described below with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of thepresent invention. It will be understood that each block of theflowchart illustrations and/or block diagrams, and combinations ofblocks in the flowchart illustrations and/or block diagrams, can beimplemented by computer program instructions. These computer programinstructions may be provided to a processor, in particular amicroprocessor or a central processing unit (CPU), of a general purposecomputer, special purpose computer, or other programmable dataprocessing apparatus to produce a machine, such that the instructions,which execute via the processor of the computer, other programmable dataprocessing apparatus, or other devices create means for implementing thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

The flowchart and block diagrams in the figures illustrate thearchitecture, functionality, and operation of possible implementationsof devices, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblocks may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustrations,and combinations of blocks in the block diagrams and/or flowchartillustrations, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention are apparent from and will befurther elucidated, by way of example, with reference to the drawings,in which:

FIG. 1 is a block diagram of an embodiment of the systems of theinvention and of an embodiment of the electronic device of theinvention;

FIG. 2 is a flow diagram of a first embodiment of the first method ofthe invention;

FIG. 3 is a flow diagram of a first embodiment of the second method ofthe invention;

FIG. 4 is a flow diagram of second embodiments of the first and secondmethods;

FIG. 5 is a flow diagram of a first embodiment of the third method ofthe invention;

FIG. 6 is a flow diagram of a third embodiment of the first method;

FIG. 7 depicts an example of a lighting system installed in threeadjacent rooms;

FIG. 8 is a flow diagram of a third embodiment of the second method;

FIG. 9 is a flow diagram of a second embodiment of the third method;

FIG. 10 depicts an example of a light network comprising ten luminaires;

FIGS. 11-13 depict examples of dynamically assigning network nodes tofunction groups;

FIG. 14 depicts an example of a time-varying allocation of a node tofunction groups; and

FIG. 15 is a block diagram of an exemplary data processing system forperforming the method of the invention.

Corresponding elements in the drawings are denoted by the same referencenumeral.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows embodiments of the systems and the electronic device of theinvention. In the embodiment of FIG. 1, the bridge 1 combines thefunctionality of the system for controlling message routing within awireless network of the invention and the system for selecting one ormore devices in a wireless network for transmitting, receiving and/orprocessing a radio frequency signal for presence and/or locationdetection of the invention. In an alternative embodiment, the bridge 1only implements one of these two functionalities. In a differentembodiment, the systems are implemented in different types of devices.Each system may comprise one or multiple devices.

In the embodiment of FIG. 1, two electronic devices of the invention areshown: lighting devices 11 and 12. Three other lighting devices areshown in FIG. 1: lighting devices 13, 14 and 15. The lighting device 11is a Hue go luminaire, the lighting device 12 comprises LED strips, thelighting device 13 is a ceiling lamp, the lighting device 14 is afloor-standing lamp and lighting device 15 is a table lamp. In theembodiment of FIG. 1, Lighting devices 13-15 are not configured toperform RF-based sensing or asset tracking in a first part of a periodand obtain network messages in a second part of this period, unlikelighting devices 11 and 12. In an alternative embodiment, lightingdevices 13-15 are, similar to lighting devices 11 and 12, alsoconfigured to perform RF-based sensing or asset tracking in a first partof a period and obtain network messages in a second part of this period.Bridge 1 and lighting devices 11-15 form a wireless mesh network and arealso referred to as nodes.

The bridge 1 comprises a processor 5, a transceiver 3, and a memory 7.The processor 5 is configured to determine a first subset of thelighting devices 11-15. The first subset comprises one or more devicesthat are assigned a radio frequency-based presence and/or locationdetection function. The processor 5 is further configured to determine aplurality of routes from a source node to a destination node. At leastone of the plurality of routes comprises one or more intermediate nodes.The processor 5 is further configured to select one of the plurality ofroutes based on how many of the intermediate nodes of each of theplurality of routes are part of the first subset of the plurality ofnodes and use the transceiver 3 to transmit one or more messages tocause the wireless mesh network to perform message routing according tothe selected route.

In some wireless standards, e.g. Zigbee, various routing mechanisms canbe available and/or active. Some of these are determined by the sendingdevice (source routing: the sender instructs the path to be used for themessage), some of these are determined in a distributed fashion (AODVrouting) where the nodes in the Zigbee network build up routing tablesbased on sent and received messages. In the former case, the processor 5can instruct (e.g. via Manufacturer Specific messages) a sending deviceto use a specific route. In the latter case, the processor 5 couldinfluence the routing e.g. by sending Manufacturer Specific messages toinstruct the various Zigbee nodes to influence this distributed processin such a way that the preferred routes as described in the previousparagraph are accomplished (or encouraged) and/or unwanted routes areavoided (or discouraged), e.g. by deliberately adjusting routing cost.Another mechanism could be where the role (NCN/BRM) of nodes, andpossibly the role of neighboring devices, is used to influence therouting decision the nodes make (and/or routing costs the nodesannounce), and thus also influence the routing decision of neighboringdevices.

The processor 5 is further configured to determine a suitability of eachof the lighting devices 11-15 for transmitting, receiving and/orprocessing a radio frequency signal for presence and/or locationdetection, select a subset of devices from the plurality of devicesbased on the suitability determined for each of the plurality ofdevices, and instruct at least one of the subset of devices to act as adevice for transmitting, receiving and/or processing a radio frequencysignal for presence and/or location detection. The payload of thetransmitted wireless message, from which the receiving lights candetermine the RSSI utilized in the RF-based sensing, may include thereporting of the RSSI data of other messages which the transmittingdevice itself has received earlier from other devices in the network.Hence, the RF-based sensing messages may not have just dummy payloadsbut payloads with a meaning.

The lighting devices 11 and 12 comprise a processor 25, a transceiver23, a memory 27, and a light source 29. The processor 25 is configuredto use a first protocol to transmit and/or receive a radio frequencysignal during a first part of each of a plurality of periods. The radiofrequency signal is used for presence and/or location detection. Theprocessor 25 is further configured to obtain network messagestransmitted wirelessly using a second protocol during a second part ofeach of the plurality of periods. The second part does not overlap withthe first part. A duration of the first part varies between at least twoof the plurality of periods and/or a duration of the second part variesbetween at least two of the plurality of periods.

RF-based presence detection is also referred to as RF-based sensing.RF-based sensing may be used if a target needs to be detected that doesnot carry a dedicated transmitter or receiver and does not transmit orreceive any signal. RF-based localization (or location detection) isalso referred to as RF-based asset tracking (the asset may be an object,animal or person, for example). RF-based asset tracking may be used if atarget/asset needs to be detected and/or located that carries orincorporates a dedicated transmitter or receiver. The asset beingtracked may receive or transmit BLE beacons, for example. RF-basedsensing offers the possibility to detect motion or presence by analyzingthe dynamic variation of diagnostic data and communication parameters ofa wireless communication system, such as e.g. received signal strengthor other network diagnostics data (e.g. number of retries until amessage is successfully delivered) changes on the wireless links betweendifferent nodes of a network.

In the embodiment of the bridge 1 shown in FIG. 1, the bridge 1comprises one processor 5. In an alternative embodiment, the bridge 1comprises multiple processors. The processor 5 of the bridge 1 may be ageneral-purpose processor, e.g. ARM-based, or an application-specificprocessor. The processor 5 of the bridge 1 may run a Unix-basedoperating system for example. The memory 7 may comprise one or morememory units. The memory 7 may comprise one or more hard disks and/orsolid-state memory, for example. The memory 7 may be used to store atable of connected lights, for example.

The transceiver 3 may use one or more communication technologies tocommunicate with the light devices, e.g. Zigbee, Thread and/orBluetooth, and/or one or more wired or wireless communicationtechnologies to communicate with a wireless LAN/Internet access point(not shown), e.g. Ethernet or Wi-Fi. In an alternative embodiment,multiple transceivers are used instead of a single transceiver. In theembodiment shown in FIG. 1, a receiver and a transmitter have beencombined into a transceiver 3. In an alternative embodiment, one or moreseparate receiver components and one or more separate transmittercomponents are used. The bridge 1 may comprise other components typicalfor a network device such as a power connector. The invention may beimplemented using a computer program running on one or more processors.

Some of the functions performed by the bridge 1 in the embodiment ofFIG. 1 are performed by an Internet server in an alternative embodiment.This is especially beneficial for more sophisticated RF-based presencedetection algorithms or RF-based people counting. For security class usecases, a longer latency (e.g. 10 seconds) is typically acceptable, whilefor lighting class use cases (e.g. switching the lights on) a latency of0.5 seconds or less is desirable, making a round trip to an Internetserver potentially problematic.

In the embodiment of the lighting devices 11 and 12 shown in FIG. 1, thelighting devices 11 and 12 comprise one processor 25. In an alternativeembodiment, the lighting devices 11 and 12 comprise multiple processors.The processor 25 of the lighting devices 11 and 12 may be ageneral-purpose processor or an application-specific processor. Thelight source 29 may comprise one or more LED diodes, for example. Thememory 27 may comprise one or more memory units. The memory 27 maycomprise solid-state memory, for example.

In the embodiment shown in FIG. 1, a receiver and a transmitter havebeen combined into a transceiver 23. In an alternative embodiment, oneor more separate receiver components and one or more separatetransmitter components are used. In an alternative embodiment, multipletransceivers are used instead of a single transceiver. The transceiver23 may use one or more wireless communication technologies tocommunicate with bridge 1, e.g. Zigbee, Thread and/or Bluetooth. Thelighting devices 11 and 12 may comprise other components typical for alighting device such as a power connector. In the embodiment of FIG. 1,the two electronic devices of the invention are lighting devices. In analternative embodiment, the electronic devices of the invention areother types of devices, e.g. non-lighting devices which are related tothe lighting system (such as wireless sensors and switches that could beused for the presence/location detection), or other non-lightingdevices.

A first embodiment of the method of selecting one or more devices fortransmitting, receiving and/or processing a radio frequency signal isshown in FIG. 2. A step 101 comprises determining a suitability of eachof a plurality of devices for transmitting, receiving and/or processinga radio frequency signal for presence and/or location detection. A step103 comprises selecting a subset of devices from the plurality ofdevices based on the suitability determined for each of the plurality ofdevices. A step 105 comprises instructing at least one of the subset ofdevices to act as a device for transmitting, receiving and/or processinga radio frequency signal for presence and/or location detection. Step105 may further comprise instructing at least one of the subset ofdevices to transmit network messages, e.g. messages of a lightingcontrol system (e.g. reporting of power consumption).

A first embodiment of the method of controlling message routing within awireless (e.g. mesh) network is shown in FIG. 3. A step 111 comprisesdetermining a first subset of the plurality of nodes. The first subsetcomprises one or more devices that are assigned a radio frequency-basedpresence and/or location detection function. A step 113 comprisesdetermining a plurality of routes from a source node to a destinationnode. At least one of the plurality of routes comprises one or moreintermediate nodes. A step 115 comprises selecting one of the pluralityof routes based on how many of the intermediate nodes of each of theplurality of routes are part of the first subset of the plurality ofnodes. A step 117 comprises transmitting one or more messages to causethe wireless mesh network to perform message routing according to theselected route. These steps may be performed in the manner previouslydescribed in relation to the bridge 1 of FIG. 1.

Second embodiments of the method of selecting one or more devices fortransmitting, receiving and/or processing a radio frequency signal andthe method of controlling message routing is shown in FIG. 4. In thissecond embodiment, the methods of FIGS. 2 and 3 are combined. After step101, a step 121 is performed which comprises both step 103 of FIG. 2 andstep 111 of FIG. 3. Step 111 may be the same step as step 103 or step111 may comprise selecting an even narrower subset of devices from thesubset determined in step 103, for example. After step 121, steps 113and 115, as shown in FIG. 3, are performed.

After step 115, a step 123 is performed, which comprises both step 105of FIG. 2 and step 117 of FIG. 3. Step 105 may be the same as step 117,i.e. the one or more messages instruct the at least one of the subset ofdevices to act as a device for transmitting, receiving and/or processinga radio frequency signal for presence and/or location detection. Thus, asingle message both instructing a device to perform (or not to perform)RF-based sensing or asset tracking and comprising routing instructionsmay be transmitted to a single device. Alternatively, step 117 maycomprise transmitting different messages, e.g. to change the routingprotocol of one or more network nodes. Next, after a certain time orevent, step 101 or step 121 may be performed again, for example. As afirst example, steps 101,121,113,115 and 117 may first be performedduring commissioning and later again after commissioning and after use.As a second example, steps 101,121,113,115 and 117 may first beperformed during commissioning and steps 121,113,115 and 123 may laterbe performed again after commissioning and after use.

A first embodiment of the method of obtaining network messages of theinvention is shown in FIG. 5. A step 141 comprises using a firstprotocol to transmit and/or receive a radio frequency signal during afirst part of each of a plurality of periods. The radio frequency signalis used for presence and/or location detection. A step 143 comprisesobtaining network messages transmitted wirelessly using a secondprotocol during a second part of each of the plurality of periods. Thesecond part does not overlap with the first part. A duration of thefirst part varies between at least two of the plurality of periodsand/or a duration of the second part varies between at least two of theplurality of periods.

This method may be performed by lighting devices 11 and 12 of FIG. 1,for example. The system of the invention, e.g. bridge 1 of FIG. 1, mayinstruct a network node to perform the method of the invention andpossibly how to perform the method of the invention. This instructionmay be transmitted as part of step 123 of FIG. 4, for example. In analternative embodiment of the system of the invention, none of thenetwork nodes perform the method of FIG. 5.

A third embodiment of the method of selecting one or more devices fortransmitting, receiving and/or processing a radio frequency signal isshown in FIG. 6. This third embodiment is used in an RF-based sensing(presence detection) application. In the embodiment of FIG. 6, one ormore of the following criteria may be assessed to determine thesuitability of each individual device in step 101 during commissioning:

Hardware-Capability Related Criteria

Participation in RF-based sensing typically requires the transmitter tosend extra wireless messages and the receiver to perform RSSI (ReceivedSignal Strength Indication) analytics and storage. This requiresadditional processing and memory resources and it is thereforebeneficial to assess available processing and memory resources.

For instance, the first generation of Philips Hue light bulbs uses aless powerful microcontroller than the newest generation of Philips Huelight bulbs. The latter has more memory and processing resources to beable to run algorithms for RF-based sensing and store more signatures(these signatures allow the changes in RSSI to be classified, e.g. todetermine the presence of a human) or run several detection algorithmsin parallel (e.g. a first algorithm is lighting-grade occupancydetection with low latency, while a second algorithm is a security-gradealgorithm with high confidence, which alerts the home owner that someoneis present in the house while the owner is away). Two identical huebulbs located in the same area may still have different operational use.For example, a first lamp has just one scene stored on it and thereforemore free memory compared to a second lamp with 30 scenes stored on it.The number of scenes on a lamp is not a static parameter and typicallychanges over life of the lamp since the user/system may change it. Theamount of available memory may change with software updates of the lamp.

Criteria on Luminaire Types which have Suitable RF Characteristics, e.g.Produce a Suitable Wireless Beam Shape for RF-Sensing

Different luminaire shapes and RF designs lead to different RFcharacteristics, e.g. wireless beam shapes. For instance, a ceilingluminaire with a glass surface has a different wireless beam shape thana metal-cone table lamp. The same wireless lamp placed within a firsttable-top luminaire with a metal cone-shape shield will result in anarrower wireless beam pattern compared to a second table lamp withidentical luminaire outline, but a fabric textile shield. It istherefore beneficial to classify the luminaires with respect to their RFcharacteristics, e.g. RF-based sensing characteristics. This can be donewith model identifications of luminaires (e.g. “Philips Hue Beyond Whiteluminaire”) or the user uploading a photo of the luminaire in which alamp is placed. The sensing characteristics of the luminaire may bedetermined by analyzing the shape and the materials or by looking themup in a database. Since the same luminare can be mounted in differentenvironments and RF performance can depend on differences in theenvironment, e.g. the distance to a concrete floor above the luminaireand the presence of metal pipes above the office ceiling, it isbeneficial to also measure the real RF performance after commissioning.

Interference- and Reachability-Related Criteria.

Assessing interference- and reachability-related criteria makes itpossible to avoid lighting devices that are likely to suffer or havebeen determined (e.g. based on historical data) to suffer from wirelessinterference caused by non-lighting devices affecting the lightingdevice's ability to perform RF-based sensing. For instance, a lightingdevice which is located near other devices with an RF transmitter (e.g.a TV or WiFi access point) or which emit RF radiation might suffer fromdisturbances. For example, microwaves and power tools emit RF radiationas spurious by-product. The location of entertainment devices such asTVs with respect to Philips Hue lights may be determined based on themapping provided by the user when setting up Philips Hue Entertainmentfeature, based on images captured by a camera, based on the names of thelights (e.g. “TV light”), based on a Building Information Model (BIM),or based on a 3D model of a room, for example.

Preferably, lights that are too close to each other, e.g. two lights inthe same compact space, are not included in the same group (oftransmitting device and one or more receiving devices). For example, iffive spots can be fitted into a luminaire, it is beneficial not to pairtwo of them, as it is very unlikely any human would generate a detectionsignal between them.

Reachability refers to the link status between two devices whichsometimes can communicate directly and sometimes not—e.g. due to a metaldoor between them being closed or open. Such links are not preferred forRF-based sensing unless the RF-based sensing is used to monitor whetherthe automatic fire door is closed or open (which has value to preventthe spread of a fire).

End-User Usage-Pattern Related Criteria

-   -   Assessing end-user usage-pattern related criteria makes it        possible not to select a lighting device that is often        transitioning between on and off (e.g. a sensor-controlled        closet light) versus lighting devices which are on most of the        day. The latency introduced by RF-based sensing is much more        noticeable for humans when the lights transition from off to on        (e.g. the user might have walked too far into a room and        collided with furniture in the dark) than on to off.    -   Assessing end-user usage-pattern related criteria makes it        possible not to select those lighting devices which a user uses        most for dynamic light scenes (especially those scenes requiring        low latency).    -   Assessing end-user usage-pattern related criteria makes it        possible to select a lighting device that is more often on than        off. As RF sensing would introduce some delays due to        processing, an external trigger meant to set the light to on        could have a noticeable delay if the light was previously off        compared to if it already is on.

Criteria on Locally Available Spare Data-Rate in a Certain LocalSub-Part of the Network or Certain Device

-   -   If there is insufficient headroom (i.e. the spare data-rate is        low) in the network to send the additional RF signals between a        controller and a paired lamp, which are required to obtain a        good RF-based sensing performance, this controller is not very        suitable for RF-based sensing. For instance, the Zigbee radio of        the controller has to handle lots of traffic as it is talking        (i.e. transmitting and/or receiving non-RF-sensing related        traffic) to all lights. Transmitting non-RF-sensing related        traffic may comprise transmitting light control commands or        backhauling high-bandwidth sensor data from the lights, for        instance a PointGrab sensor transmitting rich and highly        accurate metrics to the gateway about the number of occupants in        a room and additional context such as the work tasks performed        in the room. Transmitting and/or receiving non-RF sensing        related traffic may further comprise polling, reporting,        gathering sensor data, and/or pushing data between different        network sections, for example. The controller's aggregator        function may lead to it having less available Tx/Rx resources,        while other Zigbee nodes in the same network (and even in        proximity to it) would not have these issues. Hence, for larger        networks, the Zigbee radio of the controller may already be at        maximum capacity and the controller may not be a good candidate        for forming an RF-sensing pair with a wireless light, in        particular not for transmitting RF signals for RF-based sensing;        occasionally sharing aggregated RSSI data may in some        circumstances be still possible. However, the controller may be        a good candidate to serve as the listening part of RF-sensing        pairs, i.e. to record the RSSI of messages it receives from each        of the lights. Each of the lights may record the RSSI of all        messages sent by the controller regardless whether the message        is addressed to this specific light. However, it is not        desirable to load the radio of the controller to capacity as        otherwise unwanted lighting-control latency is introduced in the        system (other pairs of lights may be filled to maximum wireless        capacity as they are not latency critical from the application        perspective).    -   Selection of those lamps which fulfill a critical role in the        network communication path between two sub-areas of a building        or building floor or to the controller (e.g. one light in the        staircase is a critical router for the system to communicate        with the media room upstairs) should preferably be avoided.    -   While a first lamp transmits, a second and third lamp can record        the RSSI. Whether the second or third lamp reports out the RSSI        by sharing it with the coordinator of the RF-based sensing group        may depend on the choices made during commissioning of the        RF-based sensing group. Not only the headroom of the first lamp        is important. The second lamp may be at a certain distance from        the first lamp and may have a different headroom than the first        lamp. When the second lamp reports out its RSSI, also its        headroom is important. It hence may be advantageous to assign        the lamp with the biggest headroom as the transmitting device of        the RF signal for RF-based sensing, while the other devices with        less bandwidth predominantly listen to the messages and only        occasionally report out aggregated RSSI data. If the RF signals        used for RF-based sensing have a short duration, then the        transmitting device does not need to be the device with the        biggest headroom. In this case, it may be advantageous to assign        the lamp with the biggest headroom as receiving device of the RF        signal for RF-based sensing, as in this case, the probability is        highest that the receiving device(s) is not transmitting or        receiving other signals while the transmitting device is        transmitting the RF signal for RF-based sensing.    -   If in an commercial office application, several WiFi enabled        gateways are used per floor and each of them is backhauling the        data from a subset of the Zigbee lights to the cloud and large        amounts of RF-based sensing data are backhauled to the cloud,        e.g. for advanced machine learning and analytics (e.g. people        counting), then those lights connected to a gateway with the        largest spare capacity for the cloud backhaul are most suitable.    -   Different sensing rates may be assigned to sub areas of a space        (e.g. a high rate to those areas that require automatic light-on        behavior while other areas in the space with light already being        on have lower message rates). Typically, in RF-based sensing        algorithms, each of a plurality of transmitting devices        transmits an RF signal once per loop. However, it is possible to        increase the sensing rate in specific areas by letting a        transmitting device transmit an RF signal multiple times per        loop. For example, in a normal situation, each sensing loop        would get messages from nodes 1,2,3,4,5. The sensing rate may be        increased in certain sub areas by changing the sensing loop to        1,2,2,2,3,4,5,5,5, where nodes 2 and 5 would be extra snappy,        e.g. as they are closer to the entrance. These different sensing        rates should preferably be taken into account when determining        the available bandwidth in a network and on this basis assessing        the suitability of a device.

Spatial Criteria

Philips Hue lamps are normally grouped per room. It is therefore known,assuming the user used some logical criteria for grouping, which roomeach lamp is in. However, the Hue system does not know the full-layoutof the building (e.g. house) or building floor. Unlike other sensingtechnologies, RF-based sensing can also consider use of lamps near(rather than in) the occupancy-sensing target area (e.g. within anadjacent room) and can still successfully perform occupancy mapping ofthe first room. In a Philips Hue system, a typical room comprises, froma RF-based sensing perspective, many different types of luminaires dueto e.g. luminaire placement, height, luminaire type etc. Often twoadjacent bedrooms have the similar types of luminaires present (e.g. oneceiling light, one table light, and strips at floor height.)

For improved performance, the determining of the suitability of a devicefor RF-based sensing takes into account where within each room and atwhich relative altitude the lights are positioned. For instance, in athree-bedroom first floor of a residence, as depicted in FIG. 7, twoceiling luminaires 51 and 52 may be assigned to perform RF-based sensingfor room 41 (room A), while for room 42 (room B) adjacent to room 41(room A), the two table top lamps 54 and 55 are assigned for theRF-based sensing, and for room 43 (room C) the LED strips 57 under acouch/TV. Due to differences in placement and type of the luminaires,the recorded RF-based signatures differ significantly, such that iftransmissions between the two ceiling luminaires 51 and 52 in room 41(room A) cause the system to see a high RSSI signal in Room 41 (room A),the transmissions between the two ceiling luminaires 51 and 52 in room41 (room A) may also cause the system to see an attenuated—but stillhigh—RSSI in room 42 (room B).

Normally, this would have triggered a false positive in room 42 (roomB), but since room 42 (room B) intentionally does not use the ceilingfor RF-based sensing, but rather leverages the table top lamps 54 and55, which have a different general shape of the luminaire and differentattenuation, it is easier to identify and disregard false positives. Itmay be advantageous, depending on how the RF-based sensing isimplemented, to not select for the RF-based sensing a ceiling and tablelight that are within the occupancy detection target area, but ratherselect a table lamp in the target area (not shown) combined with anothertable lamp located in the adjacent room, e.g. table top lamp 54 or 55,as the lights at same altitude will result in the optimal RF-basedsensing resolution, because a table light is mostly surrounded by airwhile a ceiling light faces on one side a potentially RF reflectingsurface formed by the concrete ceiling with its iron. In somesituations, ceiling lights may be least obstructed by other objects suchas office furniture and hence constitute the best location forperforming RF-based sensing. If millimeter wave (Extremely HighFrequency) radio technology is used, then it is important that there isa line of sight path between the lamps, because this radio technology isvery directional.

Furthermore, devices far away from drainage pipes (water mass offlushing toilet water can cause false triggers), swinging trees with wetleaves and pedestrian walkways in homes that lead directly to street arepreferred.

It may be beneficial to avoid luminaires which give false triggers dueto people walking in the corridor outside of the room. If not possibleor not desirable, a trigger from such a luminaire may be used as a firststep in a two-step occupancy detection process (e.g. the first triggeris generated by a luminaire close to the corridor and this first triggerlowers the detection threshold of a luminaire which is located furtherwithin the room but still close to the first luminaire; this two-stepprocess enables detecting of people entering the room well).Furthermore, different weights may be assigned to such a luminaire sothat only a larger motion than the one needed inside the room cantrigger a detection outside.

Suitability of Devices to Perform People Counting (Versus MerelyDetection of Room being Occupied/Unoccupied)

People counting is not always about an accurate count, but sometimesjust about distinguishing between two or a few levels of occupancy in aroom. For instance, knowing whether a room is moderately busy or verybusy will make it possible to proactively (instead of reactively)increase the airflow of the Heating, Ventilation and Air Conditioning(HVAC). Hence, with RF-based sensing, it is possible to get a bit morecontext info about a space than before. For people counting, therequirements on the RF-based sensing are higher than for mere detectionwhether the room is occupied/unoccupied.

Suitability of lights to determine the spatial location of bio mass overtime (e.g. to track people or forklift with driver in warehouse; largesquare with a grid of site & area luminaires)

As wireless communication signals are heavily absorbed by water,RF-based sensing is a detector for the presence of bio mass (i.e. bodywith lots of water). Hence, for instance in a manufacturing site,RF-based sensing performed by a regular ceiling grid of WiFi equippedluminaires can track employees. In addition, large metal surfaces suchas forklifts will reflect the wireless signals and hence the changecaused by the presence of a forklift between two luminaires can bedetected and positively linked to a forklift (rather than a human body).

Criteria Regarding Mounting Orientation

Assessing criteria regarding mounting orientation makes it possible toselect devices with a mounting orientation which results in suitable RFcharacteristics, e.g. RF beam shapes, with respect to a target area.Some lights, such as spot luminaires, have adjustable directions.Usually, the direction of the luminaire is set once by the user duringinstallation of the fixture and then never adjusted. For instance, ametal shaped spotlight may be turned upwards, downwards or left orright. Depending on the orientation of the spot, the directionality ofthe RF transmission and its propagation into the space from within themetal cone will greatly differ.

If the wireless beam is oriented to the target area, e.g. using amillimeter wave (EHF) radio or a WiFi radio with (multiple) directionalantenna(s), and other RF characteristics are suitable as well, the huelamp in the luminaire may be suited for RF-based sensing, whereas if thebeam is pointing to the ceiling the same lamp may not be suitable (evenif other RF characteristics are suitable). Mobile luminaires may offerthe user different orientations of the luminaire (e.g. a cube-shapeluminaire for decorative lighting), which result in different RFcharacteristics, e.g. RF-beams, depending on where the radio is at thatmoment located. These orientations can be easily detected internallye.g. with onboard sensors like gyroscopes or externally e.g. by the useof cameras.

Various Criteria Especially Relevant for Luminaires

-   -   Placement of driver. Any wireless driver which is placed        in/around/surrounded by metal is not preferred due to its impact        on RF performance. For example, wireless drivers close to major        metal things such as HVAC duct or close to metal wiring or close        to structural elements such as columns and steel frames are        preferably avoided. A driver in a lighting device is a circuit        that mainly transforms input mains or DC voltage supply bus        (e.g. 48V or high-voltage DC from solar) into a controlled        voltage to get the light source(s), e.g. LEDs, to shine. A        wireless driver also has a radio, such that the resulting        luminaire can communicate wirelessly. Drivers do not need to be        near the light source(s). For example, the light source(s) may        be hanging from the ceiling, while the driver that powers the        light source(s) is behind the ceiling. This can lead to        different RF performance than expected.    -   The type of the housing of the luminaire. A plastic luminaire        housing is preferred over a perforated metal luminaire housing        and a perforated metal luminaire housing is preferred over a        continuous metal luminaire housing. Although metal can sometimes        help in shaping RF signals, normally, the closer the driver is        to free air, the better. Metal is (for RF purposes) almost the        opposite of free air.    -   The direction and size of the openings in the luminaire. For        WiFi based RF-based sensing, a higher frequency WiFi (5 GHz) is        preferably assigned to those luminaires with smaller openings in        the metal.    -   The direction in which the radio/luminaire is facing. Suspended        office luminaires are often located right above the work desk at        eye height and have often two independent light sources for        up-lighting towards the ceiling and downlighting towards the        task area of the desk. These two light sources may be controlled        by two independent LED drivers both equipped with a wireless        radio. The wireless LED driver with upward facing radio is        preferred over the one with downward facing LED driver, for        instance, as it is further away from the office furniture which        includes many metal beams and metal surfaces leading to        reflections of the wireless signals. In addition, the position        of objects such as chairs may affect the absorption of wireless        signal and introduce changes to the baseline signal. The        wireless LED driver on the top surface of the luminaire faces        upward towards a column of air and hence the wireless signal        propagates in a well predictable and reproducible fashion.

In the embodiment of FIG. 6, the suitability of a device is alsodetermined by determining a suitability per group of devices. This isperformed in sub steps 161-164 of step 101. Each group comprises atleast two devices, typically a transmitting device and one or more, e.g.two to four, receiving devices. Step 161 comprises selecting a pluralityof groups of devices. All devices which were selected after assessingthe above-mentioned criteria may potentially be included in a group. Allselected devices within a certain distance of each other may be grouped.Several devices may collaborate with each other. These devices thenrecord the RSSI of RF signals transmitted by some or all of the otherdevices in the same group. In this case, the RSSI of the devices in thegroup are assessed in order to decide whether a space is occupied ornot. Thus, a group comprises 2+ devices where some or all 1:1connections (‘pairs’) between those devices might be used.

More devices than immediately required may be selected. These sparedevices may be selected in/for one or more detection areas where nodesare likely to be depowered, such as an area of table lights with on/offswitch. For example, six devices may be employed to cooperate for theRF-based sensing instead of four devices. While this results in highernetwork load and higher uC load, this will ensure that the detectionarea still works when one or two devices, e.g. lights, are depowered (itis not known upfront which device will be depowered in the next event).

Step 162 comprises determining whether there are two groups of theplurality of groups that have a device in common and target a same oradjacent sensing area. In other words, step 162 comprisesdetermining/picking mutually exclusive devices, e.g. luminaire, groups.If this determination is positive, one of the two groups is determinednot to be suitable. One disadvantage of RF-based sensing is that aperson is in room A near the wall to room B causes wireless disturbancealso in room B. Hence, in prior art RF-based sensing the confidence forallocating the user to the correct one of the two rooms suffers.

When performing RF-based sensing for the entire house or (part of) abuilding (=not just one single target detection area, but multipletarget detection areas), it is beneficial to assign the RF-based sensingfunction in a way so that the two groups of lights used for RF-basedsensing in adjacent rooms are mutually exclusive groups (i.e. one lightcan only be part in one of the two adjacent RF-based sensing group).Picking mutually exclusive luminaire groups ensures that the RF-basedsensing signals of the two different groups of lights look as differentas possible. This reduces the likelihood that a poor detection in room Agets “stolen” by room B and hence reduces ambiguity and false occupancydetection positives.

The same principle may be used when groups comprise more than twolights, e.g. one transmitting light and multiple receiving lights. Thesame light should not be the controller performing all the RF-basedsensing algorithmic processing for multiple groups in order to bettershare the load. However, a non-controller node, which (a) records theRSSI of the messages it hears and (b) reports out the RSSI, mayparticipate concurrently in two different groups. In this case it notjust reports out the RSSI of RF signals received by the first group oflights but also the RSSI of the second group of lights.

Step 163 comprises determining whether a communication quality between apair of the plurality of devices is below a certain threshold. If thisdetermination is positive, this pair is determined not to be suitable.The communication quality typically depends on whether there areobstacles blocking the RF-based sensing path. RF-based sensing methodsdo not necessarily require direct line of sight between the devices.However, wireless signals cannot see through certain obstacles. Forinstance, if the end-user re-arranges a large of piece of metalfurniture (e.g. bookshelf), the RF-sensing path between the devices maybe compromised.

The communication quality may be considered to be below the certainthreshold when a change in the static signal path has resulted in abroken detection path between the pair of devices, e.g. lamps 1 and lamp2. To detect a broken RF-based sensing path, the system may compare acurrent RF signature of a room with an RF signature of that roomsomewhere late at night (e.g. 2 am) when it is very likely that there isno contribution from people present in the detection area or when it isknown that all occupants are out of home.

The communication quality may be below the certain threshold even whennormally, devices are able to communication with each other. If thesignal is weak, a potential temporary obstruction such as provided by ahuman body in the way would then mean that the path effectively breakstemporarily. It is therefore beneficial to measure/estimate thecommunication quality while taking into account the worst-case scenario,which would also include the obstruction provided by a human body. Instep 164, the devices of the remaining (i.e. suitable) groups aredetermined to be suitable. Step 162 may be performed duringcommissioning and after commissioning and step 163 may be performedafter commissioning, for example.

After steps 101, 103 and 105 have been performed during commissioning,the normal operation of the system may start, i.e. RF-based presenceand/or location detection may be performed in step 166 by the at leastone device instructed in step 105. In step 167, it is checked whether acertain time has passed and/or another criterium has been met andtherefore the suitability of the devices needs to be re-evaluated (i.e.after commissioning). If not, then RF-based presence and/or locationdetection may be continued in step 166. If so, then step 101 may beperformed again.

For example, it may be checked in step 167 whether the weather has(significantly) changed. For instance, if RF-based sensing is applied inthe exterior garden lighting (e.g. for people counting) and the systemknows there is snow falling now, which may influence the transmission ofwireless signals, it may be beneficial to select different lights forthe RF-based sensing. During fair weather, the mains powered lightmounted on the wall of the house 5 meters away from the garden door maybe used to do RF-based sensing. During snowfall, the battery operatedgarden light which is located right next to the garden door may be usedto do RF-based sensing. Similar, fog or rain are known to attenuatewireless signals.

The suitability of the devices may also be re-evaluated when theRF-based sensing mode is switched, e.g. between people counting, peoplelocating, detecting human entrance into an empty room, and security. Forexample, people counting is not a time critical feature. It is normallyperfectly acceptable to spend e.g. 10-30 seconds to conclude that thereare three persons in a room. Based on certain selection criteria, itmight be concluded at a first moment that luminaires 1,2,3,4 are thebest for lighting control as they are the ones that provide immediatedetection when people enter the room. However, the system can beconfigured in layers, such that the application's goal is first todetermine if there's someone in the room (to switch on the lights) andonly later to count how many people there are.

As such, the easiest way is to have the system constantly running inmotion sensing mode as that leads to the lowest latency. Once there iscertainty that there is at least one person in the room, the system canautomatically switch over to people counting mode, as that provides therichest information. However, perhaps lights 1,2,3,4 are not the idealones for people counting as e.g. they are not in the center of the roombut close to the entrance. The system can then select luminaires to e.g.3,4,5,6,7 for RF-based sensing, as they are the ones optimized forpeople counting. The same applies to switching over between lightingcontrol mode (e.g. during day) and security mode (at night or duringweekends and holidays).

In the second iteration of step 101 (which is performed aftercommissioning), a further suitability of each of the plurality ofdevices for transmitting, receiving and/or processing the radiofrequency signal is determined. In the second iteration of step 103, afurther subset of devices is selected from the plurality of devicesbased on the further suitability determined for each of the plurality ofdevices. In the second iteration of step 105, at least one of thefurther subset of devices is instructed to act as a device fortransmitting, receiving and/or processing a radio frequency signal forpresence and/or location detection.

In the embodiment of FIG. 6, one or more of the following criteria maybe assessed to determine the suitability of each individual device instep 101 after commissioning:

History on Network-Reachability

Assessing the history on network reachability makes it possible to avoidassigning lamps with bad history on network-reachability the task ofperforming RF-based sensing.

-   -   A user may be more prone to switching a certain lamp off with        the legacy wall switch i.e. depowering the wireless lamp and        hence making it incapable of performing RF-based sensing. It is        better not to use this lamp for RF-based sensing.    -   Certain lamps occasionally have poor reachability due to        wireless interference (e.g. when the same 2.4 GHz band is used        by an audio streaming system in the neighbor's apartment).

If in a mesh network the media room can only be reached by meshing vialamps 1 and 2 located in the kitchen area and lamp 1 has bad historicalreachability, e.g. because the user uses the legacy wall switch often,is it best not to select lamp 2 as RF-based sensing node to avoidcritical-path issues for the core lighting control commands to reach themedia room unless lamp 2 is a critical light for RF-based sensing. Forexample, if there are no other candidates and messages to the media roomare not entirely filling the network, it may still be good to selectlamp 2 as RF-based sensing node. In this case, although lamp 2 issuitable as RF-based sensing device, it may be assigned to the RF-basedsensing task less of its time than other devices. Lamp 2 may thus beconsidered suitable, but less suitable than other devices, and thedegree of RF-based sensing performed by a device may depend on itsdegree of suitability. The time spent by lamp 2 on RF-based sensing maydepend on whether it is used for streaming of light commands toaccompany audio and/or video content.

Controlled by a Motion Sensor, Battery Operated Switch, or Mains PoweredZigbee Switch

Assessing whether a device is controlled by a motion sensor, batteryoperated switch, or mains powered wireless (e.g. Zigbee) switch makes itpossible to favor lights as RF-based sensing nodes which are controlledby either a motion sensor, battery operated switch, or mains poweredZigbee switch. It is less likely that these lights are switched off by auser than those lights using a legacy wall switch, which disrupts thepower to the wireless lamp.

Real-Time Wireless Interference-Related Criteria

Assessing real-time wireless interference-related criteria makes itpossible to avoid lamps which currently suffer from wirelessinterference caused by non-lighting devices and other lighting systems(and hence would affect a lamp's ability to perform RF-based sensing),while in the same location but at a later time assessment of thiscriterion might result in them being considered valid candidates toperform RF-based sensing

-   -   A lamp, which is located near other radio-equipped consumer        electronics devices (e.g. a TV or WiFi access point), will        suffer from disturbances as soon as the consumer electronics        device is switched on, or video streaming over WiFi starts.        However, when the TV is off, the lamps close to the TV will not        suffer from interference and hence the lamps are fine candidates        to perform RF-based sensing. The location of entertainment        devices such as TVs with respect to Philips Hue lights may be        determined based on the mapping provided by the user when        setting up the Philips Hue Entertainment feature. The real-time        status of the TV (on vs. off) may be retrieved by the Philips        Hue system via an API of the TV or an API of a home automation        system (e.g. Apple Homekit/Apple TV or Google Home), for        example.    -   Additionally, interference may originate from another lighting        system. For instance, a lamp located in proximity to the        neighbors' living room may suffer from wireless interference        from the neighbors' mesh lighting network which may for instance        be operating on the same Zigbee channel, or occasional periods        of video streaming over WiFi to his TV such as used by e.g.        ChromeCast.

End-User Usage-Pattern Related Criteria

-   -   Assessing end-user usage-pattern related criteria makes it        possible not to select the lamp that is known by the system to        often transition between on and off (e.g. a sensor-equipped        walk-in-closet light which requires instant switching on of the        light) versus a light in the staircase which is most of the day        on (or even an emergency light which is always on). The latency        introduced by RF sensing is much more noticeable for humans when        the lights transition from off to on (e.g. the user might then        walk too far into a room and collide with furniture in the        dark).    -   Assessing end-user usage-pattern related criteria makes it        possible not to select those lamps for RF based sensing which a        user uses most for lighting dynamic scenes (especially those        lamps participating in scenes requiring low latency).        Criteria on Current Freely Available Data-Rate within the        Overall Wireless Network

In a large Zigbee network comprising hundreds of lights, the trafficcaused by the Zigbee router devices sending their link status every 15seconds may already consume 15% of the total Zigbee airtime budget.Typically, this immediately leads for large-scale networks to a shortageof bandwidth whenever the system has to perform a new temporary task ontop of the normal basic system tasks (e.g. OTAU firmware update, runninga dynamic tunable white lighting scene, high-resolution RF-basedsensing, entertainment streaming). Hence, in a large-scale network, lessdevices may be selected for RF-based sensing roles and suitabilityrequirements are preferably applied stricter and based on accurateinformation. For smaller networks (e.g. a network comprising 30 wirelesslights), more airtime headroom is available for the lights performingadditional tasks such as RF-based sensing.

Currently Available Free Airtime within the Zigbee Network

Which group of lamps is the optimal choice for the RF-based sensingnormally depends on the currently available free airtime within theZigbee network. Participation in RF-based sensing typically requires thetransmitter to send extra wireless messages or other signals and thereceiver to determine the RSSI and other network diagnostic parametersand then perform RSSI (Received Signal Strength Indication) analyticsand storage. For instance, a link between lamps A and B best may givebest occupancy detection results only at highest data rates (e.g.Philips Hue entertainment mode is running). If only a low bandwidth isavailable between the lamps (e.g. due to crowded spectrum), a linkbetween lamps B and C may be best suited to perform the occupancysensing.

Typically, links between a single transmitting device and multiplereceiving devices are assessed for RF-based sensing. Typically, anRF-based sensing group comprises three to five lamps sending messagesand determining the RSSI of received messages from the other lamps. Oneof the lamps may be assigned to do the processing of the occupancydetection algorithms, while the other lamps just send messages andreport out the RSSIs to the one lamp doing the presence detectionprocessing algorithm.

Forecasted Free-Airtime within the Zigbee Network

By forecasting the free-airtime within the Zigbee network (based oncontext), it is possible to proactively adjust the selection of lamps toperform the RF-based sensing. Often, a lighting system knows upfrontthat additional network loading will be coming up due to situations suchas (1) a specific schedule (e.g. dynamic scene scheduled at 8 pm) (2)sensed parameters which are known from history to subsequently causesome peak loading (e.g. a person entering the media room at 08:30 likelymeans he will watch TV with dynamic Ambilight surround-lighting) (3) aschedule software update cycle (OTAU). In these cases, it is beneficialto proactively adjust the selection of lamps performing the RF-basedsensing accordingly.

For example, the lighting system predicts that entertainment lightingscene will soon be activated in the media room. The system knows thatthe light in the staircase will become a critical Zigbee router for thecontroller/bridge to communicate with the entertainment lighting in themedia room upstairs. The system hence does not select this lamp asRF-based sensing node or does not select this lamp for transmittingadditional RF signals specific to RF-based sensing and/or for performingprocessing specific to RF-based sensing.

Selection of those lamps which fulfill a critical role in the networkcommunication path between two sub-areas of a building or building flooror to the controller (e.g. one light in the staircase is a criticalrouter for the system to communicate with the media room upstairs)should preferably be avoided as well. In special circumstances, thelight in the staircase may already have determined a communicationpattern from its lighting-controls related messages which is frequentand well distributed over time, making this lamp suited for RF-basedsensing without the need to add RF-based-sensing-specific extra messagesor signals.

Possibility of Modifying Parameters or Delaying Actions

Devices of which the parameters or actions can be modified/delayed arepreferred, because this may ensure that there is a near-perfect RF-basedsensing. For instance, when performing an OTAU of a light's firmware,the lighting system is preferably able to adapt the OTAU speed in such amanner to leave sufficient bandwidth to execute the currently requiredRF-based sensing mode for each of the occupancy-detection target areas.Alternatively, the timing of reporting of non-latency-criticalparameters such as energy consumption and temperature may be modified tomaximize the RF-based sensing performance.

Amount of Free Processing Power Currently Available

Assessing the currently available processing resources of devices makesit possible to selects lamps which have sufficient amount of freeprocessing power currently available to ensure fast processing of theRF-based sensing data and detection algorithms; several detectionalgorithms may run in parallel, for instance a lighting-class detectionalgorithm with low latency and a security-class algorithm for detectingintruders in a vacant home with very high detection reliability buthigher latency.

For example, if the processing time of the RF-based sensing signalsexceeds 0.2 seconds, the latency of the lighting controls may beunacceptable for the end-user (especially in cases the lights had beenoff and need to be activated based on the occupancy sensing). Twoidentical hue bulbs located in the same area may still have differentoperational use. e.g. a first lamp has just one scene stored on it andtherefore has more free memory compared to a second lamp with 30 scenesstored. The number of scenes on a lamp is not a static parameter and maychange over life of the system. Also, the available free processingpower will vary from lamp to lamp, for instance a lamp running a complexlight effect with a built-in microwave sensor will have less free CPUresources than a static lamp.

In a Philips Hue system, some bulbs act as Zigbee parent node for Zigbeeend-nodes. Being a parent node consumes additional resources (e.g.processing, data storage, regular radio contact with end-node) comparedto non-parent bulbs. Typical Zigbee end-nodes are battery-operateddevices such as wall-switches and sensors or battery-operated lights.The Zigbee end-nodes dynamically choose their parent based on the bestwireless link. Hence, the parent device of the Zigbee end-node maychange several times over life. Hence, assigning a Zigbee parent-deviceand a Zigbee end-device to a single RF-based sensing group may not beadvantageous. In addition, RF-based sensing typically requiresadditional RF signals and/or processing and hence will shorten thebattery life of a Zigbee end device.

If RF-based sensing is used for multiple applications, e.g. security andlight control, multiple algorithms typically need to be performed.Although it would be ideal if one device could process both algorithms,a device may also be considered suitable if it is able to perform one ofthe multiple algorithms. In this way, the responsibility may be splitsuch that all the devices which would be suitable in view of othercriteria are not ignored, but the available processing power criteriagets split among multiple nodes instead of an all or nothing approach.This may be used when algorithms are “stacked”, e.g. determining quicklythat there is motion is algorithm A, but taking a deeper look andconcluding presence with a much higher degree of confidence at theexpense of higher latency is algorithm B. An application might want toget both results out, but due to this stacking a situation could bereached where a node is suitable for running either A or B, but notboth.

On/Off Status of the Lights

By assessing the on/off status of the lights, it is possible to optimizethe stand-by power of the lighting system during RF-based sensing.Typically, a device needs somewhat more power during transmission thanreception (which is the idle state of a router lamp device, independentof whether the light is on or off). Hence, transmitting heavy wirelesstraffic for RF-based sensing while the light is “off” might increase theconsumed power (which could be considered “standby power” because thelight is off). To meet potential future more stringent standbyregulations, it may be advantageous to predominantly select lights toperform RF-based sensing which are currently on, i.e. emitting light (ifpossible).

Current Thermal Stability

By assessing the current thermal stability of lamps, it is possible toselect lamps which are currently thermally stable to perform RF-basedsensing. A lamp's temperature might drift when the operational state ischanged between lights on/lights off. This results in temperature driftof the radio electronics, which results in drifting of the wirelesstransceiver characteristics (e.g. receiver sensitivity). Selectingthermally “stable” lamps will hence result in smaller offsets betweenradios than utilizing a light that has just transitioned betweenlights-off and lights-on. In the case of lamps which are more thermallyunstable, these drifts/offsets could fool the system to believe that thedynamic characteristics of the environment have changed, potentiallyleading it to conclude that there has been motion (this being a falsepositive).

Exposure to Daylight

During the day, certain lights will never be switched on as sufficientnatural light is available in their specific area. These lights areexcellent candidates for RF-based sensing, as they are not expected tobe switched on by the user and hence—despite of the lamps being off—donot require low latency to lighting controls commands. If these lamps doget turned on, the amount of daylight already present would help maskthe effect of potential latency issues when compared to anotherpreviously dark room transitioning to on. It is therefore beneficial toselect lamps with a high exposure to daylight. However, while somelights may be excellent RF-based sensing nodes during the daytime, theymay be a poor choice during night time (e.g. low latency controlrequired for this space). Lights which are always on (e.g. used incorridors without windows or in areas of a building where there isalways someone during office hours) are also good candidates. Generally,lights which do not switch from OFF to ON a lot or are good candidatesif latency is a concern.

Lighting Command Transmission Activity

By assessing the lighting command transmission activity, it is possibleto assign lamps which are currently less active in sending lightingcontrols commands to be more active in taking care of the listening- andprocessing- and storing associated with the RF-based sensing. Highlyinteractive lamps e.g. lights in an (active) entertainment group, shouldnot be assigned to perform basic chores for RF-based sensing that can beallocated elsewhere in the system. For instance, the lights in theentertainment group (which render light to accompany audio and/or videocontent) create (or receive) a lot of traffic, which is good for RFsensing, but they should primarily be focused on providing perfectlighting experience to the user. One option is to assign a light whichis part of an entertainment group to perform RF-based sensing, but tolet the data storage and CPU intensive data analytics processing beingdone by a light which is not part of the entertainment group. Forexample, the device that transmits the entertainment light commands maybe the transmitting device in multiple RF-based sensing groups. Theother device(s) in these groups may be lights inside or outside theentertainment group, for example.

Criteria on Currently Available Spare Network Data-Rate

By assessing the currently available spare network data-rate, it becomespossible to select devices with sufficient currently available sparenetwork data-rate. For instance, a Zigbee radio within acontroller/bridge may be currently performing a OTAU firmware upgrade ofthe lamp in the kitchen. Combined with the normal lighting controltraffic with the other lights in the house, the radio in thecontroller/bridge currently handles a lot of wireless traffic. Hence,the Zigbee radio residing within the controller/bridge may already be atcapacity and may not be a good candidate right now for forming anRF-sensing group with the wireless light in the living room (until thefirmware update of the kitchen light has finished). One option is toassign the controller/bridge to still participate in the RF-basedsensing, but to let the data storage and CPU intensive data analyticsprocessing being done by a light which is not part of the OTAU upgradeand hence has ample of free computing power and memory.

RF Characteristics, e.g. Beam Shapes, with Respect to the OccupancyDetection Target Area.

By assessing the RF characteristics, e.g. beam shapes, with respect tothe occupancy detection target area, it is possible to select luminairesof which the current physical position results in suitable RFcharacteristics, e.g. beam shapes, with respect to the occupancydetection target area. For instance, a cube-shaped battery-operatedluminaire (similar to a Hue Go) may have six different faces and theuser may be able to select the orientation of the cube. If the facecontaining the radio chip, e.g. WiFi radio chip or 60 GHz mm-wave radiochip, is at that moment oriented to towards the target detection area,it makes the cube luminaire well suited for RF-based sensing. If theradio is facing the floor, the luminaire is not well suited to performRF-based sensing.

The suitability of a luminaire positioned in a certain orientation mayalso depend on other material in its surrounding. For instance, if it ison a metal table, the cube being oriented downwards will yield poorresults for RF-based sensing, while if the table is made from thin wood,the RF-based sensing still can be performed satisfactorily. If a radiochip is incorporated into a light bulb and this light bulb is placed ina metal luminaire, this may result in directed RF performance as well,even if the RF performance of the radio chip itself, e.g. a Zigbee radiochip, is uniform.

On these last few pages, a first set of criteria has been described foruse during commissioning and a second set of criteria has been describedfor use after commissioning. Some criteria are present in both sets.Although some other criteria are only present in one of the sets, theymay be usable both during commissioning and after commissioning.Criteria that have been described in relation to RF-based sensing(motion detection or true presence detection or fine-grained sensingcapable of detecting body postures or gestures) may also be usable forRF-based asset tracking (localization).

While the selection criteria above are used to avoid certain lamps toperform RF-based sensing in the embodiment of FIG. 6, it is alsopossible to throttle the RF-based sensing on purpose to mitigate thenegative system impact of the RF-based sensing described above. In theextreme case, the RF based sensing can be throttled to the extent thatjust the non-sensing related messages sent within the Zigbee network areused.

A third embodiment of the method of controlling message routing within awireless, e.g. mesh, network is shown in FIG. 8. As described inrelation to FIG. 3, the aim of this method is to determine which nodesto instruct to perform network routing, i.e. forward the messages thatthey receive. These instructions result in the network routing beingadjusted and the wireless spectrum being freed up locally for theexecution of RF-based sensing and/or asset tracking and have beendescribed in more detail in relation to the bridge 1 of FIG. 1.

As previously described, step 111 comprises determining a first subsetof the plurality of nodes and this first subset will comprises one ormore devices that are assigned a radio frequency-based presence and/orlocation detection function. This first subset may be selected manuallyor automatically.

The first subset may be selected from all nodes or from nodes that aredetermined to be suitable for RF-based presence detection and/orlocalization as described in relation to FIGS. 2 and 4, for example. Ifthe one or more nodes of the first subset need to perform RF-basedlocalization (RF-based asset tracking), then selecting one node may besufficient. If the one or more nodes of the first subset need to performRF-based presence detection (RF-based sensing), which is more difficultto perform than RF-based asset tracking and in which the to be detectedobjects, persons or animals do not carry RF transmitters and/orreceivers, then typically at least one group of at least two nodes isrequired and these nodes are then typically selected based on the of oneor more target sensing areas.

Next, a second subset of the plurality of nodes is selected based on thelocations of the one or more nodes of the first subset in step 172.While the one or more nodes of the first subset will transmit and/orreceive one or more radio frequency signals for the radiofrequency-based presence and/or location detection function, the one ormore nodes of the second subset will not. Instead, the one or more nodesof the second subset will try to limit the interference caused to theRF-based presence and/or location detection by not re-transmitting somenetwork messages or any network messages, e.g. lighting controlcommands, intended for other nodes (in this embodiment, the sensingand/or asset tracking RF signals are transmitted in-band). The one ormore nodes of the second subset might receive the RF signals forRF-based presence and/or location detection, but do not need to and/ordo not need to record their RSSI. A node of the second subset may beincluded in the second subset instead of the first subset due to it notbeing in a suitable location or not adding additional information beyondwhat is already possible with the other nodes. Next, step 173 comprisescreating a third subset of nodes that consists of the remaining nodes ofthe plurality of nodes (i.e. not selected as part of the first subset orthe second subset). Unlike the one or more nodes of the second subset,the one or more nodes of the third subset re-transmit all networkmessages intended for other nodes, i.e. perform the normal routingfunction.

As previously described in relation to FIG. 3, step 113 comprisesdetermining a plurality of routes from a source node to a destinationnode. Step 115 of FIG. 3 comprises a sub step 175. Step 175 comprisesselecting one of the plurality of routes based on how many of theintermediate nodes of each of the plurality of routes are part of thefirst subset or the second subset of the plurality of nodes. Step 117comprises transmitting one or more messages to cause the wireless (e.g.mesh) network to perform message routing according to the selectedroute. This has been described in more detail in relation to the bridge1 of FIG. 1.

In step 117, these one or more messages are normally transmitted using adifferent protocol (e.g. Zigbee) than the protocol (e.g. Bluetooth) usedto perform the RF-based presence detection and/or localization. In theembodiment of FIG. 8, the one or more nodes of the first subset and theone or more nodes of the second subset are instructed not to performmessage routing (e.g. for lighting control commands or regular network“housekeeping” messages) or to limit the message routing that theyperform. Furthermore, the one or more nodes of the first subset areinstructed to perform RF-based presence and/or location detection. Thenodes of the second subset are instructed to interfere with the nodes ofthe first subset as little as possible. The nodes of the third subsetare instructed to perform network routing, i.e. forward the messagesthat they receive that are intended for other nodes.

These instructions result in the network routing being adjusted and thewireless spectrum being freed up locally for the execution of RF-basedsensing and/or asset tracking. The one or more nodes of the first subsetand the one or more nodes of the second subset may be instructed to actas (e.g. Zigbee) router nodes with reduced functionality (also referredto as mode 2 later in this description), which means that the nodeslisten on the Zigbee mesh network for messages directly addressed tothem, but the nodes do not forward messages from other Zigbee nodes.

Alternatively, the one or more nodes of the first subset and the one ormore nodes of the second subset may be instructed to act as (e.g.Zigbee) end-nodes (also referred to as mode 3 later in thisdescription), which do not participate in the mesh network at all butonly check every certain period (e.g. 0.5 seconds or longer) formessages destined for this node received and temporarily stored by theirparent node(s). Alternatively, the one or more nodes of the first subsetmay be instructed to act as router nodes with reduced functionality,while the one or more nodes of the second subset are instructed to actas end-nodes, or the other way around, for example. The nodes of thethird subset act as full-fledged (e.g. Zigbee) meshing nodes (alsoreferred to as mode 1 later in this description), thereby providing thebackbone for a robust building-level, e.g. mesh, network.

In the embodiment of FIG. 8 or in an alternative embodiment, the one ormore nodes of the first subset that need to transmit an RF signal forRF-based sensing may be instructed to transmit the RF signal during acertain period without interruption, e.g. transmitting the RF signalfull blast without caring about being reachable by other nodes, and thenodes of the first subset that need to receive the RF signal forRF-based sensing may be instructed to receive the RF signal during thiscertain period without interruption. This is referred to as“high-spatial-resolution” sensing mode. If these nodes of the firstsubset are lighting devices, then this mode may be selected for thecertain period or the certain period itself may be selected independence on an expectation that the light devices are expected to stayunchanged in light output state during this certain period.

After steps 111, 172, 173, 113, 115 and 117 have been performed duringcommissioning, the normal operation of the system may start, i.e.RF-based presence and/or location detection and/or network routing maybe performed in step 176 by the devices instructed in step 117. In step177, it is checked whether a certain time has passed and/or anothercriterium has been met and the first and second subsets need to bere-selected. If not, then RF-based presence and/or location detectionmay be continued in step 176. If so, then step 111 may be performedagain and a new selection of one or more nodes of the first subset andone or more nodes of the second subset is performed.

The first and second subsets may need to be reselected when the targetsensing area used for RF-based sensing (presence detection) changes.Step 177 may comprise detecting whether user activity has changed or isexpected to change and therefore presence needs to be detected in adifferent target sensing area. For example, the routing in the networkmay be dynamically adjusted when a target person moves from first areain the house to a second area. The person thus takes ashigh-intensity-RF-based-sensing “halo” with him to the new area. Inother words, the (e.g. lighting) system adjusts the routing to now freeup wireless spectrum for RF-based sensing for the second area, while“releasing” additional spectrum for lighting controls in the first area.Additionally, as wireless signals may propagate between the first andsecond area, this approach assures that the first and second area do notunnecessarily interfere with each other.

Two examples of routes being determined between the devices of FIG. 1are now provided to help explain the method of FIG. 8. As a firstexample, the table lamp 15 and the floor-standing lamp 14 in the livingroom 32 are performing a high-resolution RF-based sensing scan to countthe number of occupants for context-awareness purposes. At the sametime, the LED strips 12 are used in the media room 33 to perform adynamic entertainment effect requiring considerable (e.g. Zigbee)traffic between the bridge 1 (located in the entrance area 34) and themedia room 33. The distance between the hue bridge 1 in the entrancearea 34 and the media room 33 is such that the (e.g. Zigbee)communication requires at least one network hop in between the tworooms.

By adjusting the routing in the network such that the table lamp 15 andthe floor-standing lamp 14 do not participate in the forwarding of theentertainment messages from the bridge 1 to the LED strips 12, the tablelamp 15 and the floor-standing lamp 14 are able to focus theirprocessing resources and/or message transmissions and/or listening forwireless commands (Zigbee devices typically cannot talk and listen atsame time) on performing the high-resolution RF-based sensing. The tablelamp 15 and the floor-standing lamp 14 may become a Zigbee end-node or aZigbee router node with reduced functionality, for example. It is alsopossible that only the node assigned to predominantly listen forRF-based sensing purposes is assigned to become a Zigbee end-node andthat this node only reports out the RSSI statistics when contacted bythe Zigbee parent device.

On the other hand, the ceiling lamp 13 in the Kid's bedroom 35 steps upand provides the routing for the entertainment traffic to the media room33. In addition, even the battery-operated Hue go luminaire 11, normallyacting as (e.g. Zigbee) end device, may be utilized as routing node(despite of increased energy consumption) in order to keep traffic awayfrom the living room 32 in which the high-resolution RF-based sensingscan is performed. There are two logical routes between bridge 1 and theLED strips 12: via the Hue go luminaire 11 and the ceiling lamp 13 orvia the floor-standing lamp 14. Since the floor-standing lamp 14 isinvolved in the high-resolution RF-based sensing scan, the route via theHue go luminaire 11 and the ceiling lamp 13 is selected, even though atypical routing algorithm might select the route via floor-standing lamp14 since this involves fewer hops.

As a second example, the table lamp 15 and the LED strips 12 areperforming a high-resolution RF-based sensing scan in the media room 33and a network route from bridge 1 to LED strips 12 needs to bedetermined. There are nine routes between bridge 1 and LED strips 12:1-14-12, 1-14-13-12, 1-14-15-12, 1-11-13-12, 1-11-13-14-12,1-11-13-14-15-12, 1-11-14-12, 1-11-14-13-12 and 1-11-14-15-12. Lightingdevice 15 has been assigned the RF-based sensing function and istherefore included in the first subset of nodes. In order to preventinterference to the high-resolution RF-based sensing scan,floor-standing lamp 14 should preferably not perform network messagerouting and is therefore included in the second subset of nodes Sincethe table lamp 15 has been included in the first subset and thefloor-standing lamp 14 has been included in the second subset, the routevia the Hue go luminaire 11 and the ceiling lamp 13 (1-11-13-12) isselected.

In the above examples, the determination of the first subset only takesinto account whether nodes are assigned an RF-based sensing function ornot. By further taking into account the resolution of the RF-basedsensing scan (e.g. major motion detection vs. minor motion detection vs.true presence detection vs. people counting), as currently required,when determining the first subset, the selected routes can be adapted tothe current requirements even better. High-bandwidth RF-based sensingwill be required for minor motion detection so that the sensingalgorithm can with confidence determine whether the variation ofwireless communication parameters with respect to a previousthreshold/baseline are due to wireless channel noise or due to a persontyping on a laptop while hardly moving otherwise.

Fine grained RF-based sensing cannot only detect presence, but alsodistinguish between number of people present (or relative amount ofpeople—one, several, a lot). For fine-grained RF-based sensing, there isa tradeoff between the quantity of messages sent per second and thelatency for determining with confidence whether the space is occupied orhow many people are in there. It is therefore beneficial to adjust theamount of messages based on the combination of the required latency forthe decision making and the required confidence level (e.g. for securityclass detection of an intruder including alerting the home owner, theconfidence level needs to be much higher than for switching on thelight; in the latter case, having a false positive can easily becorrected by switching off the light again with no harm done).

True presence detection is an even finer grained version of the RF-basedbasic motion sensing, where the resolution is increased so that evenpeople sitting in a chair or stretched out on the couch can be picked upby analyzing the variation of communication parameters compared to thepreviously known empty room situation. Hence, the higher the requiredsensing resolution, the higher the data rate of the RF-based sensingrelated communication between the lights will be and the higher thestrain on the network surrounding the target occupancy detection area.

RF-based sensing can also be used for people counting. Being able todistinguish between 10 people in an area will require higher resolutionRF-based sensing than counting a maximum of 3 people per area. A“counting-many-occupants”-mode could be optimized for distinguishingbetween 10-20-30 people whereas in a “normal-mode”, RF-based sensingcould distinguish with high accuracy between 1-2-3 people in the room.

The previously mentioned “high-spatial-resolution” sensing scan may beused to determine with high confidence whether a person is in room A orB. The “high-spatial-resolution” sensing mode may also be used fortracking trajectories of people. During performing a high-spatialresolution or many-occupants RF-sensing scan, the group of lights mayenter a special “sensing-boost mode” in which 100% of their bandwidth isdedicated to the acquisition of RF-based sensing data. This may involvethe lights temporarily not being reachable by the other lights in theZigbee network, or with longer latency. The network routing may betemporarily adjusted to facilitate this “high-spatial-resolution”sensing scan or any other high-resolution scan e.g. for people counting.

Preferably, the sensing-boost-mode, as described in the previousparagraph, is performed by lights which are on and/or are in stablemode. Stable mode means that the lights are expected to stay inunchanged light output state for the foreseeable future. For instance, alight is in stable mode when a battery-operated sensor has recentlydetected motion, which means the light will remain on at least anotherfive minutes (irrespective of whether motion is detected in that period)and a 4 minutes duration of the boost mode would be acceptable from alighting controls perspective.

If the lights are currently off (e.g. in an unoccupied home), the lightsmay be switched on for safety reasons for the duration of thehigh-resolution sensing mode, for instance in the entrance area of thehouse. In an office, the RF-based sensing may be used for soft securityduring the night where once every 15 minutes the office is scanned forabnormalities. The system may falsely think that the office is empty andstart a high-resolution scan for possible intruders; however, in realityan employee has been taking a nap in the office in an overnighter. Whenthe employee gets up, the lighting system must respond to wall switcheswithin 0.5 seconds or alternatively the lights have to be on (perhaps ata low dimming level to ensure safety) while the latency-impactinghigh-resolution sensing scan is performed.

Optionally, the system leverages other sensing modalities within thehome automation system (e.g. electronic lock, PIR sensors, Apple TV) todecide whether and how (e.g. with what delay) the RF-based-sensing halo(also referred to as target sensing area) follows a user, who istransitioning from one area of the house to another. For instance, giventhe context that a person watching TV is pausing Netflix and is deemedlikely to go to toilet, the RF-based halo remains within the TV room anddoes not follow the user. If the person however goes into the kitchenand opens the fridge for more than 30 seconds to prepare a snack, theRF-based sensing halo will follow him to the kitchen. In this case, theassignment of the RF-based sensing function to devices may be performedagain and network routes may be determined again. The fridge itself maybe able to detect that the fridge has been opened for more than 30seconds, for example. Alternatively, another type of presence sensingmay be used to detect that the person or a person in general is in thekitchen for a longer time, which may cause the RF-based sensing halo tomove to the kitchen.

RF-based sensing may not only be used to detect persons, but also todetect objects. For example, RF-based sensing may be used to detectopening of fridges and doors. This context information can be useful forelderly care, for example. This helps the gathering of key data pointsthat may be used to detect changes in patterns that could indicateemerging health conditions.

In a Bluetooth Low Energy (BLE) mesh-based (e.g. lighting) network, itmay be possible to perform RF-based sensing based on interactionsbetween (1) a BLE-equipped electronics device which normally is not partof the lighting network and (2) a BLE light (or a combined Zigbee/BLElight).

In a Zigbee mesh-based (e.g. lighting) network, the RF-based sensinginteraction between a combined Zigbee/BLE light and a BLE electronicsdevice may be performed by out-of-band communication (BLE instead ofZigbee). In this case, the Zigbee spectrum (channel) used for lightingcontrol is not affected by the RF-based sensing scan, as BLE'sfrequency-hopping spread spectrum transmissions do not interfere withZigbee's direct-sequence spread spectrum transmissions, even thoughthere is some overlap between the Zigbee spectrum and the BLE spectrum.However, although the (Zigbee) network traffic does not interfere withthe (BLE) RF-based sensing scan, the nodes which perform the RF-basedsensing scan need time to perform the (BLE) RF-based sensing scan andmay not be available to receive (Zigbee) network messages during thistime if the nodes feature a single radio performing time-sharing betweenthe BLE and Zigbee network.

Wireless interference caused by non-lighting devices (e.g. TVs) affectsa lamp's ability to perform RF-based sensing. To still perform reliablepresence detection in a first noisy area of the house, the data rate ofthe RF-based sensing should normally be increased compared to a secondmore quiet area of the house with little wireless interference. Thelamps in the first occupancy detection target area would thereforeallocate more of their airtime to RF-based sensing and they would thenhave less time or no time (or resources such as CPU and memory) toperform networking routing. Accordingly, the network routing shouldpreferably be adjusted to let lights in the other part of the buildingstep up and contribute more to the lighting mesh networking canopy, i.e.help ensure that there is proper mesh network backbone for coverageeverywhere.

A second embodiment of the method of obtaining network messages of theinvention is shown in FIG. 9. In this embodiment, an electronic deviceuses a first portion of time for RF-based sensing and a second portionof time for transmitting and receiving network messages, e.g. lightingcommands. The electronic device operates in one of the following threemodes:

Mode 1) normal Zigbee router (normal mesh mode), RF-based presenceand/or location detection: no;Mode 2) Zigbee router with reduced functionality, RF-based presenceand/or location detection: yes;Mode 3) ZigBee end device, RF-based presence and/or location detection:yes.

In an alternative embodiment, only a subset of these modes may be used,e.g. modes 1+2 or mode 1+3, and/or an additional mode may be used. Anexample of such an additional mode is a mode in which the electronicdevice acts as normal Zigbee router (normal mesh mode) and also performsRF-based presence and/or location detection. When Bluetooth, e.g. BLE,is used for RF-based presence and/or location detection, this results ina loss of efficiency, because the electronic device will not receiveZigbee messages while performing RF-based presence and/or locationdetection.

As first step, a step 180 is performed. Step 180 comprises determiningwhether the electronic device performing the method is set to mode 1, 2or 3. In the embodiment of FIG. 9, bridge 1 of FIG. 1 instructs theelectronic device which mode it should use. In an alternativeembodiment, the electronic device decides by itself which mode to use,e.g. automatically or using some decision algorithm involving itsneighbors or based on a configuration setting stored in its memory. Ifthe electronic device is set to mode 2 or 3, step 181 is performed. Ifthe electronic device is set to mode 1, step 185 is performed.

Step 181 comprises selecting the first set of frequency channels. Thefirst set of frequency channels may comprise a single channel, e.g. incase of direct sequence spread spectrum, or a plurality of channels,e.g. in case of frequency hopping. In the embodiment of FIG. 9, thefirst protocol, e.g. Bluetooth, is used to transmit and/or receive theradio frequency signal on this first set of frequency channels in step141 during a first part of each of a plurality of periods. Step 183comprises determining whether the electronic device performing themethod is set to mode 2 or 3. Step 143 of FIG. 5 comprises two substeps: steps 185 and 187. If the electronic device is set to mode 2,step 185 is performed. If the electronic device is set to mode 3, step187 is performed.

Step 185 comprises receiving the network messages, e.g. lighting controlmessages, wirelessly using the second protocol, e.g. Zigbee, on thesecond set of frequency channels. This happens during the second part ofeach of the plurality of periods. The second set of frequency channelsmay comprise a single channel, e.g. in case of direct sequence spreadspectrum, or a plurality of channels, e.g. in case of frequency hopping.If the electronic device is set to mode 1, the electronic device is ableto transmit and receive network messages (e.g. lighting controlmessages) the entire time, as it does not need to transmit or receive anRF signal for RF-based presence and/or location detection.

In this case, the first part during which the RF signal, e.g. Bluetoothsignal, is transmitted and/or received for RF-based presence andlocation detection has a duration of zero seconds while the electronicdevice remains set to mode 1 which means no RF-based presence orlocalization detection is performed by this device. The duration of thefirst part is increased, and the duration of the second part isdecreased when the electronic device switches from mode 1 to mode 2 or3. In an alternative embodiment (not shown in FIG. 9), the electronicdevice transmits and/or receives an RF signal, e.g. Bluetooth signal,for RF-based presence and location detection while in mode 1 (i.e.normal (Zigbee) mesh mode; in which it also forwards received messages),but only for short time intervals.

In the embodiment of FIG. 9, step 187, which is performed if theelectronic device is set to mode 3, comprises obtaining the networkmessages transmitted wirelessly using the second protocol from anotherdevice which received the network messages on its behalf: the electronicdevice's parent node. Network messages obtained from the electronicdevice's parent node are always intended for the electronic deviceitself. Step 195 is performed after step 187.

After step 185, it is checked in step 189 whether the message receivedin step 185 is destined for the electronic device itself or for anothernode. If the message is destined for the electronic device itself, step195 is performed. If the message is destined for another node, step 191is performed. Step 191 comprises checking whether the electronic deviceis set to mode 1 or mode 2. In mode 1, the received message is forwardedin step 193. In mode 2, the received message is not forwarded, and step181 is performed next. In an alternative embodiment, a received messageintended for another node is selectively forwarded, i.e. sometimes, butnot always forwarded, instead of never forwarded.

Step 195 comprises determining whether the message obtained in step 185or 187 is a mode config message. If so, the electronic device is set tothe mode in step 197 as instructed in this mode config message. If not,the obtained message is processed normally in step 198 and step 181 isperformed after step 198. After step 197, it is checked in step 199whether the new mode is mode 1. If so, step 185 is performed next,thereby skipping steps 181, 141 and 183. If not, step 181 is performednext.

In the next iteration of step 181, optionally, a different set offrequency channels, e.g. a third set of frequency channels, may beselected than in the previous iteration of step 181. If so, then thefirst protocol is used to transmit to transmit and/or receive the RFsignal on this different, e.g. third, set of frequency channels in thenext iteration of step 141. If the RF signal is used for RF-basedsensing, then this RF signal is preferably unique within a certainspatial area. Preferably, the (e.g. Zigbee) band dedicated to RF-basedsensing is locally-unique and differs for each group of devices, e.g.lamps, performing RF-based sensing within a house or building floor.Hence, each group of RF-based-sensing devices, e.g. lamps, can transmita (e.g. Zigbee) message storm without having to take the, e.g. lighting,control network or the needs of other groups of devices, e.g. lamps,performing RF-based sensing into account. This yields optimal sensingperformance.

An RF transmitter and/or receiver with more than one function, e.g. adual radio transceiver, may be used in which one function, e.g. a BLEradio function, is used to perform step 141 and another function, e.g. aZigbee radio function, is used to perform step 143. Alternatively,multiple transmitters and/or receivers may be used to perform steps 141and 143, respectively.

As an example, the method of FIG. 9 may be used to perform RF-basedsensing in a lighting system of a house. In this example, a dedicatedZigbee channel is used for RF-based sensing and a different Zigbeechannel is used for lighting control (network messages). The lightscurrently assigned the task of RF-based sensing operate most of the timefull-blast in Zigbee RF-based sensing mode utilizing a locally unique,dedicated wireless channel (i.e. no interference with house-level Zigbeelighting network). For a small portion of the time, the RF-based-sensinglights participate in the Zigbee lighting network.

Within the lighting network, generally, such an RF-based-sensing lightmay act as sleepy Zigbee end-device (operating in mode 3) or Zigbeerouters with reduced functionality (operating in mode 2). If a lightacts as a Zigbee end device, it only occasionally (e.g. every 0.5seconds or longer) retrieves from its parent node the lighting controlmessages received on its behalf from the house-level Zigbee network. Thelight may transform from being a normal mesh node (operating in mode 1)to an end-node (operating in mode 3) upon entering an RF-based sensingscan and accordingly the light determines a Zigbee parent node.

Alternatively, the light may transform from being a normal mesh node(operating in mode 1) to a Zigbee router with reduced functionality(operating in mode 2) upon entering an RF-based sensing scan. The lightis then regularly but not constantly reachable on the Zigbee network toreceive messages from the mesh. However, the light is not contributingto routing messages from other lights on the mesh network. The lightsoperating in mode 1 provided the backbone for a robust house-level meshnetwork. In an alternative embodiment, the light may be able to becomeofficially (temporarily) unreachable on the Zigbee network whenperforming the RF-based sensing scan and the light only reports back tothe mesh network without regularly checking a mailbox at the parentdevice.

In the above example, a Zigbee channel is used to perform RF-basedsensing. It is also possible to perform RF-based sensing interactionsbased on out-of-band interactions between (1) a BLE (Bluetooth LowEnergy)-equipped consumer electronics device and (2) a dual-radio lightpre-dominantly operating in BLE mode, wherein the light interfaces withthe consumer electronics device via BLE and in this way forms aBLE-based RF-sensing pair.

It is advantageous to involve at least one consumer electronics devicein the RF-based sensing. Most lighting nodes are ceiling mounted.However, RF-based sensing between two ceiling lights limits thedetection quality of objects close to the floor (e.g. small children);consumer devices (e.g. TV, voice assistants) are located at lower heightthan lighting devices. Hence it is advantageous to include consumerelectronics devices (e.g. TV) as one of the RF-based sensors, as the biomass of the human, which is to be detected by the RF-based sensing, isthen in between the ceiling light and the consumer device. As analternative to a consumer electronic device, a light device which it notceiling mounted may be involved.

When performing RF-based sensing with a consumer electronics device, thelight and the CE device are not necessarily required to form a network.For instance, the lights may analyze (using a scavenging approach) theRSSI of BLE advertising sent out by each CE device. The light may alsotrigger the BLE device to send out messages on purpose. For example, thelight sends via a BLE join request which in the end is not accepted bythe light, but nevertheless triggers a response which can be used forsensing, as it contains RSSI embedded in it.

While the lights that perform a low-resolution RF-based sensing scan inone area of the house may do this in the standard Zigbeelighting-control band used by the lighting system, lights performing ahigh-resolution scan may utilize another dedicated wireless band.Preferably, the frequency channel choice for each of the lights takealso into account the currently required RF-based sensing resolution foreach of the occupancy-detection target areas, notably whether majormotion detection vs. minor motion detection vs. true presence detectionvs. people counting vs. body posture detection vs. gesture detection isrequired.

High-bandwidth RF-based sensing will be required for minor motiondetection or people counting or for the “high-spatial-resolution”sensing mode, which is used to determine with high confidence whether aperson is in room A or B. Hence, the higher the required sensingresolution, the higher the data rate of the RF-based sensing relatedcommunication between the lights will be. In addition, spreading out theRF-based sensing messages over time (i.e. equally distributing them onthe time axis) will result in best occupancy detection as there are noprolonged blind periods. While regular RF-based sensing may be 3messages per second per device, high resolution scans may employ 10messages per second or even 100 messages per second.

Wireless interference caused by non-lighting devices (e.g. TV) affects alamp's ability to perform RF-based sensing. To still be able to performreliable presence detection in a noisy area of the house, normally,either the data rate of the RF-based sensing will need to be increasedcompared to a second more quiet area of the house or the wirelesschannel for RF-based sensing needs to be changed.

As different areas of the house suffer from different wirelessinterference sources, it is advantageous to select a dedicatedrelatively “quiet” wireless channel for RF-based sensing for each of theareas. The chosen out-of-band wireless channel for a specific area mightchange over time. For instance, for each RF-based sensing session, thechannel may be newly determined. This may even be done during onesensing session. The out-of-band channel may be changed if the sensingresults obtained are not as accurate as expected. However, choosing anew channel may lead to some latency since the baseline for the newchannel needs to be determined.

It may even be that the system deliberately tries multiple out of bandchannels for an area (incl. evaluation of the achieved sensing quality)before settling on one. For instance, the trying out may encompassanalyzing the number of false positives or false negatives of theRF-based sensing for each of the channels. Optionally, one singleout-of-band RF-based sensing scan may utilize distinctly differentwireless channels (e.g. lowest frequency 802.15.4 band vs 802.15.4highest frequency band) in order to increase the accuracy of theoccupancy detection by fusing the sub-scans. In the case of WiFi lights,different directionalities of the wireless transmissions may be employedutilizing the multiple directional antennas available in a modern WiFiradio.

In the case of a light of which the physical position can be easilymodified (e.g. Philips Hue Go), the selection of the out-of-band channelmay be based on a combination of (1) the accuracy of immediatelyprevious RF-based sensing sessions (2) onboard sensors in the light thatgive a certain confidence on whether or not the light has recently beenmoved or rotated.

Additionally, two different RF-based sensing pairs of lights pairs canopt to utilize the same out of band channel. For instance, the lightsmay conclude that given (1) the physical characteristics of the involvedluminaires (luminaire placement height, material of the luminaire) (2)parameters of the involved luminaires, which can be modified andinfluence the RF-based sensing (e.g. radio transmit power; open orclosed lid of a luminaire, thermal stability), the respective motionsignatures generated by the two pairs of lights will be sufficientlydifferent, so that despite of the interference between the two RF-basedsensing groups, reliable occupancy detections still can be performed.This could be relevant for areas where few suitable out-of-band channelsare available (e.g. apartment building in New York City with many of the2.4 GHz bands crowded).

Although the description on the last few pages describe an RF-basedsensing (presence detection) application, some of the describedprinciples may also be applicable to an RF-based asset tracking(location detection) application. On the next few pages, a thirdembodiment of the method of obtaining network messages in an RF-basedasset tracking application is described. However, some of the describedprinciples may also be applicable to an RF-based sensing application.

In addition, in some embodiments, the same lighting system may performboth RF-based motion/presence sensing (for objects without beacons) andasset-tracking of BLE equipped assets. In some embodiments, the sameobject such as a hospital crash cart or an employee with a BLE-beaconequipped badge is both detected by the RF-based sensing system and theBLE asset tracking system and both of the sensing modalities may bemerged by the lighting system in order to improve the location accuracyand response time to the crash cart movements. The beacon transmissionsdescribed in this system may also include other sensing data such asasset temperature, orientation of the asset (setting a flag if themedical container ever turned upside down), battery status of a medicalcool box.

In this third embodiment, ten luminaires 201-210, labelled L1-L10 andshown in FIG. 10, are grouped into different groups of luminaires thatoperate in different modes. The composition of the groups changes overtime and as a result, the amount of RF-based asset tracking and theamount of message forwarding performed by a luminaire changes over timeas well. Bluetooth Low Energy (BLE) beacons, e.g. beacon 219, have beenattached to assets, e.g. objects, animals and/or persons, in order toallow their locations to be determined.

The controller, e.g. bridge 1 of FIG. 1, assigns a first group G1consisting of luminaires 201-205 (L1-L5) in beacon receiver mode (BRM).The beacon receiver nodes collect the BLE beacons and determine the RSSIof the signals received from BLE tags mounted on assets. At the sametime, these nodes intermittently listen to the Zigbee network (e.g.nodes in BRM mode may listen 99% on BLE and 1% listen and transmit onZigbee) for lighting-related commands and to exchange lighting-controlsdata and asset tracking related data with the controller. The timedistribution between BLE and Zigbee modes, and the frequency at whichthese devices check their parent node could be fixed, or could bevariably configured by a controller device, or could even changedynamically based on the received beacon signals (e.g. if a G1 devicedetects a ‘new’ asset it might inform its parent (or the controllerthrough its parent) right away, whereas measurements related to assetswhich are stationary in the area or are less critical devices to betracked are sent in aggregated messages at some interval). The remainingluminaires 206-210 (L6-L10) (group G2) are configured as normal Zigbeerouters (Network Canopy Mode, NCM) which have their BLE (reception)functionality deactivated or BLE functionality active only for a veryshort percentage of time.

If BRM devices would be configured as normal Zigbee routers while someof them, e.g. L1, would not be listening on the Zigbee network some/mostof the time (since they are configured to listen for BLE beacons), thismay create performance issues on the Zigbee network since the ‘normal’devices, e.g. L7, who try to send a message to L1 will typically findthat the message delivery fails since L1 is (some/most of the time) notlistening to Zigbee. The basic mechanisms in Zigbee are not prepared fordevices which are not available for some/most of the time.

Hence, all the luminaires within G1 may e.g. be configured to act asZigbee end-devices (or routers with reduced functionality) and hence not(fully) participating in the Zigbee mesh network. Each of the luminairesin G1 will choose one of the Zigbee router devices (e.g. L6) as parent,and that parent is used for Zigbee communication with the L1 device(called child). When device L7 wants to send a message to such a childdevice, L7 will send the message to the parent device L6. The parentdevice will store that message on behalf of the child, e.g. L1. Thechild L1 will typically regularly check (‘polling’) with its parent L6for any pending messages, and then retrieve and process them. A child L1which wants to send a message to any of the devices on the Zigbeenetwork will send the message to its parent L6, and the parent will takecare of further relay of the message over the Zigbee mesh to itsdestination node.

As nodes in G1 need only limited time periods to communicate on Zigbeewith their parent, they can listen for BLE messages most of the time.This approach maximizes the ability of G1 devices to performhigh-quality asset tracking of the BLE beacons. This also circumventsthe Zigbee groupcast/broadcast peculiarities mentioned above (as theZigbee communication between G2 nodes will work normally as in Zigbee,and G1-G2 communication is normal Zigbee child-parent communication).

G1 devices collect the asset tracking data and send it (possibly afterfiltering and aggregation) to other devices via their parent. Assettracking data could end up at one or more of the G2 devices, or a deviceconnected via one or more of the G2 devices. All devices also functionas the lighting network: they can be controlled from a central ordistributed intelligence. G2 devices can be reached directly since theyare Zigbee router devices. G1 devices can be reached via their parent(which is a G2 device). The same lighting Zigbee network can also beused to collect switch/sensor data from G1/G2 devices or other Zigbeedevices.

Time slots for Zigbee child-parent communication can be chosenintelligently by the child if the device has learned when the BLEbeacons typically come in and hence avoids those time slots for itsZigbee communication.

When some devices on the Zigbee network send commands to control thelighting, they will be received immediately by the router devices, e.g.L2. These will store it for the child devices, e.g. L1, and only when achild device, e.g. L1, polls its parent, it will find out about thepending message and can adapt its light level. This means that when e.g.the polling interval is set at 1 second, the light L1 will have adelayed response of between 0 and 1 second compared to the light L6. Incertain situations, the 1 second delay is acceptable, for instance, ifthe lights are on and the user presses the wall switch to dim or switchoff the lights or if another source of background lighting is alreadyswitched on in the room or if the light is switched automatically basedon motion sensors/time schedules from the system without the end-userpressing a wall switch button and expecting instant response. In thiscase, the luminaires in group G2 immediately react to the dimmingcommand (and hence provide visual feedback to the user that the press ofthe wall switch button is being processed).

The luminaires in group G1 have a delayed response. The delay between G2and G1 can be mitigated by employing faded transitions for all lights(e.g. 3 seconds fade time to off). G1 may even be configured to “catchup” with G2 once G1 has finally received the dimming command. The delaybetween G2 and G1 can be further mitigated by letting one or more of therouter devices, e.g. L6, send out a BLE message once it has a(time-critical) message for one or more of its child devices, to makethem aware they need to poll their parent. It could also include therelevant body of the time-critical message in the BLE message. Thiswould remove the latency otherwise associated with the End Devicebehavior for lighting devices.

The delay between G2 and G1 can be further mitigated by employing thefollowing mechanism to allow communication as needed for lightingcontrol, collection of data from light devices and sensors, andcollection of the BLE beacon data. When lights are off, the polling rateis increased, so the perceived switch-on latency is reduced. When lightsare on, the polling rate is reduced, as the (perceived) switch-offlatency is of lesser concern, since the lights typically switch off sometime after the last person has left the area (motion sensor) or when aperson controls the central light switch at the perimeter of the areawhilst on the way out.

BLE beacon data can be sent from L1 to L6 directly when one beacon isreceived, a number of beacons is grouped, or beacon data is even furtherprocessed (e.g. averaging a number of RSSI values from a particularbeacon into aggregated values). There is a trade-off between assettracking latency vs. Zigbee transmission time for the beacon dataretrieval from child to its parent (and hence time available for BLEbeacon listening).

Preferably, the composition of groups G1 and G2 varies over time. Thismay be achieved by rotating the function BRM⇔NCM for all the devices ingroups G1 and G2. A straight swap of function BRM⇔NCM for all thedevices in groups G1, G2 might leave the Zigbee network in aless-than-optimal state for a while, and also bring the BLE beaconreception to an initial state without knowledge of which devices arepresent (and their signal strength). Therefore, a more gradual changemay be beneficial, e.g. first increase the number of NCM nodes, firstdecrease the number of NCM nodes or keep the number of BRM nodesconstant.

Several options for a more gradual change are shown in FIG. 11. Theluminaires L1-L10 are represented by columns 201-210, respectively. As afirst option, in time periods 211-213, the number of NCM nodes is firstincreased. In period 211, each BRM/NCM group contains 5 network nodes.L1-L5 are BRM nodes and L6-10 are NCM nodes. In period 212, one node(L5) is switched from BRM to NCM. After some time, in period 213,another node (L10) is switched from NCM to BRM to bring the ratio backto the original ratio.

As a second option, in time periods 214-216, the number of NCM nodes isfirst decreased. In period 214, each BRM/NCM group contains 5 networknodes. In period 215, one node (L10) is switched from NCM to BRM. Aftersome time, in period 216, another node (L5) is switched from BRM to NCMto bring the ratio back to the original ratio.

As a third option, in time periods 217-218, a direct swap is performed.In period 217, each BRM/NCM group contains 5 network nodes. In period218, one node (L5) is switched from BRM to NCM, and at (approximately)the same time, another node (L10) is switched from NCM to BRM to keepthe original ratio. Other options may alternative be used.

Repeated application of the steps shown in FIG. 11 may be used toachieve a swap of the roles of the devices in groups G1 and G2, see FIG.12. In the example of FIG. 12, the steps 211-213 of the first option(“first increase the number of NCM nodes”) are repeated several times.In period 234, one other node (L4) is switched from NCM to BRM. Aftersome time, in period 235, another node (L9) is switched from BRM to NCMto bring the ratio back to the original ratio. In period 236, one othernode (L3) is switched from NCM to BRM. After some time, in period 237,another node (L8) is switched from BRM to NCM to bring the ratio back tothe original ratio.

In period 238, one other node (L2) is switched from NCM to BRM. Aftersome time, in period 239, another node (L7) is switched from BRM to NCMto bring the ratio back to the original ratio. In period 240, one othernode (L1) is switched from NCM to BRM. After some time, in period 241,another node (L6) is switched from BRM to NCM to bring the ratio back tothe original ratio.

The sequence of steps leading from 211 to 241 in FIG. 12 have swappedthe roles of all the involved nodes. The purpose of such swap is to beable to more accurately monitor the assets near L1-L5 at some time, andto also be able to accurately monitor the assets near L6-L10 at someother time. Hence, accurate asset tracking is possible in all locations.If no rotation mechanism were applied, accurate monitoring would only bepossible near some of the nodes but not near the others, leading to anon-equal coverage of the overall area.

Similar change methods could also be used to dynamically change to adifferent ratio of G1/G2 nodes within the system (e.g. to enhancetracking performance if a new asset has entered a space), see FIG. 13.In period 261, each BRM/NCM group contains 5 network nodes. In period262, some nodes (L1 and L5) are switched from BRM to NCM, therebyincreasing the number of NCM nodes. In period 263, each BRM/NCM groupcontains 5 network nodes. In period 264, some nodes (L7 and L10) areswitched from NCM to BRM thereby increasing the number of BRM nodes.

A changeover from router R to end-device ED (or vice versa) is notstraightforward for a Zigbee device, since the specification (apart froma mention that a device could fall back from ED to R or vice versa atjoining time if its parent has no space for it, which is not applicablehere) and typical implementations are not prepared for this. Forexample, if a device known to other devices as an ED would silentlyswitch roles and send a Route Request message, this would likely confuseother devices (because they do not expect a Route Request from an ED).This section will describe how such changeover can be performed within aZigbee system without unwanted side-effects.

For both directions of role changes (ED=>R and R=>ED), the device willsend a Leave message (so other devices in its direct neighborhood areaware it is no longer in the network; this will make them ‘forget’ aboutthe device and its role, i.e. clear all the persistent and transientinformation stored about this device). This provides astandards-compliant way to enable the change, without requiring anyadditional changes on the other devices in the network. The deviceitself will remember the Zigbee channel and other relevant networkcharacteristics such as PAN, EPID, network key, network update id, shortaddress, Trust Center address and Trust Center link key (if used), etc.So, after changing role, it can be part of the network again, and startto function in its new role. It will re-join the network using thestored network parameters and credentials.

If a centralized security mode (i.e. Trust Center) is used, the deviceneeds to announce itself (in its new role) with the Trust Center. Sincethe Leave message sent before (or the Update device message generated asa result by the parent) may be reaching the TC, it should be preventedthat the TC removes all the information about the device switchingroles. Since the orchestrator responsible for the role switching, e.g.the controller 1 of FIG. 1, may be the Trust Center itself, it couldremember which devices were nominated for role change, and uponreceiving the Leave/Update Device with status 0x02=device left from thenominated devices, the Trust Center could adapt some information aboutthis device (e.g., the device type), rather than completely removing theentry.

ED=>R: After changing role, an ED which now functions a R will startperiodically sending Link Status messages (these are normally sent at 15second intervals) to maintain its connectivity in the mesh; preferablyone such message is sent directly after rejoining the network, so otherR devices in the neighborhood can take note of the new devices. Suchother R devices who notice the newly added device has an empty list ofneighbors in the Link Status message might respond earlier (than thenormal 15 s interval) with their own Link Status message so the newdevice knows which other routers are around to set up its neighbortables—and thus get ready to communicate via the mesh.

An alternative way to quickly build up the routing tables for the devicewhich changed role could to pre-populating these tables when switchingto R, e.g.:

-   -   start with the tables from the last time it was a R (might be        outdated, some devices might no longer be a R);    -   start with an initial neighbor table suggested by the        orchestrator (who knows who is an R at this time); the        orchestrator or device might know the (historic or recent) link        costs for each connection;    -   as a first approximation, the ED node switching to R can re-use        some information from the time it was the ED, e.g. it could keep        its parent router in its NT—which will already give it        connection with the mesh—and extend the NT as it continues in        the R role.

In both cases, updating the entries (both list of neighbors and therelated link cost) based on received messages could be done in adifferent way than normally (e.g. different weights can be used toaverage the values over time, additional messages—not only the linkstatus messages—may be used to add neighbor nodes, the frequency ofsending messages may be increased), as the pre-populated devices andlink costs might be outdated and hence less ‘trustworthy’ than livedata.

Advantage of these methods (over normal ‘starting from scratch’) wouldbe to send fewer messages between the devices to populate the neighbortables. Another approach could be that an ED, during its operation asED, listens to Zigbee traffic (promiscuous mode) and thus learns whichdevices are in the neighborhood, including signal strength andaddressing information, and thus (after changing its role to R) usesthis information to start its function as R.

R=>ED: Before changing the role from R to ED, it could be checkedwhether the R is performing any functions that could be affected by theswitch, e.g. whether it is a parent for another ZED, whether it isrouting on behalf of other devices, i.e. if it has any routing tableentries (other than a many to one route to the concentrator/TrustCenter/orchestrator), and/or whether it is forwarding communication onbehalf of Green Power Devices as a proxy. If that is the case, theactions could be taken to minimize the impact of the switch. Forexample, just before switching (or sending the leave message), the Rcould send network status message with status route failure, so that anew route can be discovered; if still around when the related routediscovery is started, the router could refrain from forwarding the routerecord messages.

To address its ZED children, the switching device could send a LeaveRequest message (with Rejoin=TRUE), thus forcing the ZED child to searchfor a new parent; when still around at the time the ZED starts with theparent discovery, the switching R could refrain from responding to theNWK rejoin requests. Alternatively, the orchestrator, e.g. thecontroller 1 of FIG. 1, could take care of those switching aspects,before or after the actual switch, e.g. creating a Proxy Table entry forthe GPD on another node, sending the network status (route failure)message itself or sending a Mgmt_Leave_Request message with Rejoin=TRUEto the ZED being a child of the R about to switch.

After changing role, a R which now functions as ED will need to find aparent device. Normally, this process involves the ED sending a MACBeacon message (or NWK rejoin message), followed by responses from all Rwhich have received it (in case of the Beacon, even R in other Zigbeenetwork), and selects a potential parent from the replying R devices.This is not very efficient (in time and network load), so in addition tothe most obvious improvements, like restricting the network search tothe PANID and operational channel of the network the ED used to work onas a R, several additional improvements can be used, e.g.:

-   -   the device might remember the best (e.g. lowest link cost)        neighbors (R devices) from its previous period as R, and send a        (secure) NWK Rejoin Request to that R;    -   preconfigured suggested parent from the orchestrating device,        e.g. the controller 1 of FIG. 1, which tells the device to        change its role from R to ED; that could be also sent as a        broadcast message to the entire network. Sending such a message        would make the sending of the leave message and the parent        search obsolete. Further, receiving such a dedicated message        could allow the receiving devices to keep the non-changing        information about the switching node, e.g. the binding        information, and only purge the changing information (e.g. the        NT entries and routing table entries). This message could also        remove the need for e.g. dedicated messages to instigate route        repair;    -   in yet another implementation, rather than sending the Leave        message and then selecting the parent, the node that is about to        switch from R to ED could send a new message, which contains        both the information about the role switch, and the address of        the new selected parent (e.g. the neighbor R with the best link        cost). Sending such a message would remove the need for sending        of the Leave message and the parent search. Further, receiving        such a dedicated message could allow the receiving devices to        keep the non-changing information about the switching node, e.g.        the binding information, and only purge the changing information        (e.g. the NT entries and routing table entries). This message        could also remove the need for e.g. dedicated messages to        instigate route repair.

By default, a device leaving the network would forget (delete) controlinformation it had previously used, such as bindings, group membership,etc. Obviously, the light control would need to continue after the rolechange operation, so such loss of information should be avoided. Asfirst step, the devices can remember this information and reuse it afterchanging role. Some examples (“switch” can also be read a “sensor”):

-   -   a lamp which is controlled from a switch, and the switch sends a        Leave message: normally the switch would forget which lamp(s) it        was controlling. In a preferred implementation, the switch would        remember the list of the lamp(s) it was controlling, which could        be a list of unicast or groupcast addresses;    -   a lamp which is controlled from a switch in unicast, and the        lamp sends a Leave message: the switch will remove the lamp from        its binding table (because of the Leave message), so the lamp        (or another device, such as the orchestrator, e.g. the        controller 1 of FIG. 1,) needs to reestablish the binding;    -   a lamp which is controlled from a switch in groupcast, and the        lamp sends a Leave message: the switch will not remove the lamp        from its binding table (because it is a group being sent to), so        the lamp would need to remember its group(s) membership(s) and        associated settings.

Several of the above mechanisms (naming particular command functions)assume use of the current Zigbee standard. Obviously, one could defineextensions to the Zigbee mechanisms and messages (e.g. a “I'm switchingrole” message) and implement these on the devices to achieve a smootherchangeover (with potentially fewer messages, or faster convergence).

For a dense grid of luminaires with a small portion of the luminairesacting as beacon receiver, the RSSI beacon receiver functionality may bedeliberately rotated from a first light to a second light which is notadjacent the first light but rather further away. This ensures propertri-lateration of the asset using the aggregated RSSI data obtained inthe time period before and after the rotation.

The moment when to reverse roles between G1 and G2 may be selected basedon the least possible expected disruption to the overall application andend-user experience (e.g. when lights in a certain area are currentlyswitched on, introducing some lighting latency due to execution of therole reversal is acceptable, or respect, if some luminaires in thesystem are performing a high resolution RF-based sensing scan, the highresolution RF-based sensing scan and hence wait until it is finished).

One or more central nodes collect the RSSI data from the various nodes.Since RSSI data from the assets is collected only part-time on eachnode, the asset tracking system needs to handle the missing RSSI datasamples, and the fact that they have been sampled some time ago, and canalso exploit the combined data from multiple network nodes receivingbeacons—even though these multiple network nodes do not (actively)receive and process the beacons at the same time.

This advantageously can provide improved tri-lateration of assets and/ortheir tracking. The processing may take into account that assets may bemoving, so ‘live’ data can be considered more reliable than ‘past’ data(which may have resulted from the assets being in a different position).It may also take into account additional data regarding the movement ofassets. Example: if there is also a motion sensor in the room (PIR orRF-based sensing), and no motion is detected, likely the assets willalso not move (typically they get moved by the humans who get detectedby the motion sensor when moving). On the other hand, if there is motiondetected in a part of the area assets in that area might move within thearea, or into or out of the area. In this case, once the RF-basedsensing has detected movement, the joint RF-based sensing and assettracking system may change its focus from predominantly motion sensingto predominantly asset tracking. This is advisable, because the more thelight is listening via BLE to asset tags, the less time it can spend onperforming RF-based sensing with the Zigbee radio.

Variant 1: Directed Asset Search

Preferably, the controller, e.g. bridge 1 of FIG. 1, dynamically andadaptively assigns the (1) ratio of luminaires are acting as trackingnodes and non-tracking nodes, (2) the respective locations and (3) dutycycle for BLE vs. Zigbee (and optionally reporting strategy for ‘new’ or‘high-value’ assets vs. other assets) while taking into account:

-   -   the context of the lighting controls system (e.g. how many        lighting commands are expected in this period and what are the        lighting latency requirements)    -   the context of the data collection system (e.g. there may be        periods when a central device collects data from many devices)    -   the context of the asset tracking system, e.g.:    -   If a new asset starts has entered the room, the number of        luminaires of beacon receivers may temporarily be increased in        order to quickly obtain an accurate location fix.    -   If a moving person is being tracked, the beacon receiving        intensity of the asset tracking function in the joint system is        increased.    -   Expected movement trajectories of assets based on historical        data.

When there are indications that assets are moving or could be moving,the system can dynamically optimize the distribution of BRM/NCMfunctions to make sure BRM nodes are active near the potentially movingassets, to improve tri-lateration accuracy and/or speed.

As a first example, if there is motion detected in a part of a space(especially near a door), assets may come into or leave the space there,so enhanced asset tracking performance is desired in this part of thespace. This could be achieved by assigning additional BRM nodes(adjusting the ratio BRM/NCM for some period) or a “shift” of the BRMnodes to the area (while keeping the ratio BRM/NCM more or lessconstant).

As a second example, if a certain high-value asset is detected, more BRMnodes in that area are temporarily activated to get a faster and/or moreaccurate fix. As a third example, the allocation may be based onhistoric data for specific assets or a type of assets (cleaning trolleystypically are in other positions than emergency crash carts, and maytypically move at a different speed and pattern).

Variant 2: Transitional Mode Between NCM and BRM

To ensure Zigbee network stability at any given moment, hard swapping ofthe Zigbee router/end-device functionality between the modes should beavoided. Hence, this variant proposes a mechanism where lights graduallymigrate between the Beacon Receiver Mode and Network Canopy Mode via anadditional mode, transitional mode (TM). Devices in transitional mode(TM) are in the process of migrating between Primary-Zigbee (NCM)functionality and primary-BLE-asset-tracking mode (BRM), while takingthe needs of the networking canopy (network coverage) in mind. Devicesin mode (TM) may for instance act as Zigbee Router or Zigbee router withreduced functionality to keep the network canopy functional while stillacting as beacon receivers (e.g. 50% beacon receiver and 50% Zigbeerouting node).

Hence in this variant, the devices have three possible modes, forinstance:

-   -   Zigbee routers 100% of the time (NCM)    -   BLE receivers 99% of the time and Zigbee End Device 1% of the        time (BRM)    -   50% Zigbee routers and 50% BLE receivers part time (TM)

For the “TM” devices, it may be advantageous to:

-   -   not route traffic through such nodes since the other router        devices can communicate with them only part of the time. One        mechanism is setting the Link Cost field, in Link Status        messages and/or when forwarding Route Requests, to a high value        (meaning high cost) to discourage the other nodes to route        traffic through the TM node. Another one is to delay forwarding        of Route Request, or not forwarding them at all, which prevents        routes being constructed through the TM node.    -   let them not be the parent of a Zigbee end device, as the parent        (the TM device) may be unavailable on Zigbee when the end device        wants to communicate.

Variant 3: BRM Nodes Receive Messages, but do not Rebroadcast Messages

As alternative to defining BRM nodes as Zigbee End Devices, the BRMdevices may be commissioned not to rebroadcast messages received fromother nodes. These BRM nodes may hence act on the Zigbee network asrouter without routing functionality i.e. the BRM nodes act like aZigbee routing device only for its own traffic but is not routingmessages originating from other devices (i.e. the BRM device does notrespond to the route discovery messages of other nodes). This approachmay be advantageous over making BRM nodes Zigbee end-device, which doesnot receive broadcast directly and hence require buffering of messagesby parent nodes. The router nodes without routing functionality will notrequire buffering. It should be noted that as Zigbee end-devices arerequired to poll their parents regularity for messages, this causesadditional network traffic, and latency in sending messages to suchdevices. The “not rebroadcasting” could be selective, e.g. byrebroadcasting more important lighting control messages (such as “on”)and not rebroadcasting less important messages.

Variant 4: Additional Group of Luminaires Receives Messages, but doesnot Rebroadcast Messages

In addition to a group of nodes that are configured as normal Zigbeerouters (NCM) and a group of nodes that are configured as Zigbee enddevices (BRM), there may be an additional group of nodes that areconfigured as Zigbee router without routing functionality. Nodes in thevicinity of the BRM nodes may be put in this group in order to preventinterference to the BRM nodes, as explained in relation to FIG. 8 (wherethis group was referred to as “second subset”).

The operating mode of a node is preferably changed while the node is inuse, as described in relation to second embodiment of the method (seeFIG. 9) and the third embodiment of the method. An example of luminaireL1 changing operating modes is shown in row 201 of FIG. 14. In thisexample, luminaire L1 acts as Zigbee router with reduced (routing)functionality (operating mode 2 of FIG. 9) in periods 281 and 282, asZigbee end device (operating mode 3 of FIG. 9) in periods 283 and 284and as normal Zigbee router (operating mode 1 of FIG. 9) in period 285.

In parts 291 of the periods, luminaire L1 performs RF-based assettracking (or RF-based sensing in an alternative embodiment). In parts292-294, luminaire L1 obtains network messages. In parts 292 and 294,luminaire L1 receives network messages from normal Zigbee router nodes.In part 293, luminaire L1 obtains network messages from its parent node.In part 294, luminaire L1 further forwards network messages that itreceived and that were intended for other nodes. Luminaire L1 may alsotransmit its own network messages to other Zigbee devices (i.e. networkmessages not received from other Zigbee devices) in parts 292-294.

Variant 5: Dual-Radio Lighting Control/Asset Tracking for a Thread MeshNetwork

In this variant, the Thread protocol is used for lighting controlmessages instead of the Zigbee protocol. The Thread standard allows amaximum of 32 routers per network, with the rest of the devices beingnon-router nodes (end device). Thread describes a router node selectionprotocol based on criteria e.g. the total number of routers in thenetwork, number of neighbors, link quality with neighbors, and routertables of neighboring routers. If in Thread, one of the end devicesloses its connection to its router node, then the end device itselfstarts to search for another router. The Thread standard also describesthe mechanism for end devices transitioning to become router nodes andvice versa e.g. if an end device thinks it is better suited to become arouter, it requests to become a router. If a Thread router node stopsacting as router node (change to end device role), it informs itsrespective child devices that they have to switch to an alternativerouter node as parent.

The Thread networking standard has some functionality relevant in thecontext of this invention, compared to the Zigbee-based examplesdescribed above. In Thread, there are 2 device types and 6 device roles;the device type is fixed, while the role of devices can change overtime. The 2 types of devices are the following: (a) full Thread device(which can have one of these roles: Leader, Router, REED, FED), and (b)minimal Thread device (which can have the MED and SED roles).

The 6 roles a device can have are the following (the first three ofthese are Routers (R), the last three are End Devices (ED)):

-   -   Leader (elected router, bookkeeping, list of routers)    -   Router    -   REED (Router Eligible End Device: it could be router but is        inactive currently, i.e. working as ED; REED=FED+runs algorithm        to check if it needs to become router)    -   FED (Full End Device; FED=MED+has one parent, links to multiple        devices to receive multicast)    -   MED (Minimal End Device: has one parent, its radio is always on,        its parent expects the MED to be awake, messages are sent via        parent, and MED has no mechanisms to cope if parent message does        not successfully arrive)        -   the MED device described in the current Thread standard is            hence not suited to directly serve as a dual radio            (Thread+BLE) luminaire, as an MED needs to listen to Thread            messages constantly and has no time to listen to BLE            messages.    -   SED (Sleepy End Device: like MED, but sleepy as far as Thread is        concerned)        -   This SED is the only one which can sleep (as far as Thread            is concerned), though in the present invention, the device            may use the time it is not listening on Thread to listen to            another channel (BLE); others are always listening as Thread            device.

So, for dual radio luminaires, the BRM devices would use the SED role,and the NCM devices would use one of the “router” roles (leader, router,REED). Changing roles is allowed in the Thread spec, so changing fromSED to one of the other (router) modes and vice versa should not be aproblem like in Zigbee (see above description of Zigbee and measures towork around the issues).

One aspect to take into account is the automatic balancing of the numberof nodes of a certain type in a Thread network:

-   -   For large networks, Thread by default allocates about 23 devices        as R, rest as ED.    -   In Thread, if there are more than about 23 routers in a system,        R volunteers to become ED.    -   If there are fewer than about 23 routers in a system, ED        requests to become R.

This is an automatic allocation based on local interaction between thedevices, using a distributed algorithm. Such automatic allocation willnot result in what is desirable for a combined lighting+asset trackingnetwork, since in Thread's automatic allocation, all Thread routers maysometimes end up at the left side of the room and all ED on the rightand this hampers tri-lateration for asset tracking. Additionally, thereare no triggers in Thread to dynamically change the role over locations(which is needed to improve tri-laterations).

As described above, it is advisable to orchestrate the assignment ofrouters to obtain a suitable distribution of devices for the assettracking application. To prevent automatic assignment of Thread routers,the Thread standard already allows that a central point can tell adevice (via an out of band channel) to change role; the device theninforms it neighbors about its changed role. Hence the Thread protocolalready provides nice hooks and standard messages for this, while Zigbeelacks those messages, as explained above.

The following sequence describes how to implement the role-changingbetween NCM and BRM in a Thread system, using the roles of ThreadRouters (R) for NCM and Sleepy End Devices (SED) for BRM:

BRM=>NCM (SED=>R): An SED would first attach as a normal ED, thenupgrade to a router, then downgrade others to ED to SEDs (NCM=>BRM). Forautonomous changes, the Thread spec has delays (0-120s) forstabilization; this might be too long for the application. If suchchange were done in an orchestrated way, this could be performed withinseconds. It should be noted that change messages may lead to peaks innetwork traffic; hence Thread applies a trickle time mechanism whichgradually increases when things are stable. It is preferable to applycentral orchestration of the role changes, which enables at networklevel gradual role changes to prevent change-message traffic peaks.

In a sparse Thread network with a limited number of nodes (e.g. in aresidential applications), all Thread devices become routers after a fewminutes. Preferably, even in such a sparse Thread network, some devicesare deliberately configured as sleepy end-device SED so that they havesufficient time to listen for BLE beacons signals transmitted by theasset tags. This may require modification of the Thread stack in thesedevices if the Thread stack complies with the current Thread standard.

Variant 6: More Sparse Networks e.g. Philips Hue Network

Networks used in a professional lighting application such as office orhospital typically have many nodes, so division of the nodes into groupswith different functionality can likely be achieved without effectivelyimpacting the performance and ‘health’ of the Zigbee network.

In a sparse network, such as a home lighting application, it may be morechallenging to apply these mechanisms, as the roles need to be allocatedand changed carefully to make sure that both the Zigbee network keepsfully functional as well as the Beacon Receiving (asset tracking)functionality keeps functional with acceptable tracking performance. Onthe other hand, in such a home environment, repeated swapping the modeswap between G1 and G2 might increase location accuracy, while ensuringsufficient Zigbee network performance.

Since a typical home network has fewer nodes than a typical professionallighting application network, it is expected that the Zigbee networkload is lower, and also the number of tagged assets is lower. Therefore,one might use a few devices out of the total number of devices for BRMwhile maintaining a working Zigbee mesh with the majority of the nodesconfigured as NCM. Rotating the roles will allow to get more accuratecoverage of the asset location.

In addition, in home networks some lights may be temporarily depoweredby a mains voltage wall switch and hence temporarily cannot contributeto the asset tracking system. Hence, upon depowering of a light, thesystem reconfigures the distribution of nodes between G1 and G2 untilthe light is powered up again.

If insufficient nodes are available to perform both asset tracking andRF-based sensing in a certain area of the home, the system disables oneof the two functionalities depending on the context. For instance, ifthe home owner is out of the house, RF-based motion/occupancy sensing isperformed to monitor the house for possible intruders. If the owner isat home, the system may disable the automatic lighting control withRF-based sensing (and the user has to use the battery-operated wallswitch instead), while the system still tracks the location of a BLEequipped consumer device across the house.

Variant 7: WiFi+BLE Combined Radio

Likely, in the future, lights will be controlled with a WiFi lightingcontrol network, for instance using the 802.11s standard. WiFi chips nowalready commonly feature a BLE radio as well. Hence, this will allow fortime-shared BLE+WiFi combo radios in lights, wherein the BLE radio isused to receive beacons and WiFi provides the networking canopy.

The WiFi 802.11is standard distinguishes between router nodes and enddevices. In a WiFi solution, luminaires can either act as Mesh AP(interfacing to the user's smartphone via WiFi in a standalone networkwithout gateway) or Mesh node (no AP at the luminaire; the smartphonetalks with the central gateway).

In an embodiment, some of the WiFi lights act semi-concurrently asbeacon receivers. In this embodiment, the WiFi lights are assigned toeither act as Wifi Mesh AP node or as WiFi Mesh Node or as WiFi MeshAP+Beacon Receiver node or as WiFi Mesh Node+Beacon receiver node.

Extension 1: Take into Account the Current Lighting Latency Requirements

-   -   When the lights are off during a time of the day when electric        lighting is required or in a space without daylight, typically        no persons are present, so assets cannot move in this        space/room. Hence it is possible to increase the number of NCM        nodes within this space and/or increase the polling rate of the        BRM nodes to their parents—both with the goal of fast reaction        when the lights need to switch on. Additionally, the network        canopy of the overall system is strengthened by now having more        NCM modes from the un-occupied sub-space.        -   It should be noted that the fact that within each space            there is a mixture of NCM nodes (which will react directly)            and BRM nodes (which will react with some latency due to            required polling of the parent) will have a limited effect            on the perceived latency by the end-user, as many of the            lights (the NCM nodes) will switch on immediately, which            visually hides the fact that some nodes (the BRM nodes)            might be slower to respond. Employing a transition time (for            all nodes but especially the NCM nodes) also helps to hide            this fact. Optionally, it may be possible to smartly shorten            the dimming transition time for the BRM nodes in a way so            that the end-point of the light-fading process of the BRM            nodes coincides with the endpoint of the NCM devices,            despite starting with a delay.    -   When the lights are on, typically persons are present in the        space, so assets can move. Hence, it is beneficial to increase        the number of BRM nodes to be able to accurately track the        assets whenever the light is on in this space. Latency for light        control is of lesser concern when the light is on—typically the        lights need to be switched off some time after the last person        has left the room, so any latency impact for the switch-off        command on some nodes is likely to go unnoticed.

Extension 2: Clever Moment of Polling

A Zigbee End-Device once in a while needs to talk to its parent (butrarely) so it misses a short period of BLE beacons. Since BLE beaconsare sent in a regular pattern, it can advantageously poll its Zigbeeparent at a moment when BLE beacons from known assets in its area arenot expected.

FIG. 15 depicts a block diagram illustrating an exemplary dataprocessing system that may perform the method as described withreference to FIGS. 2-6 and 8-9.

As shown in FIG. 15, the data processing system 300 may include at leastone processor 302 coupled to memory elements 304 through a system bus306. As such, the data processing system may store program code withinmemory elements 304. Further, the processor 302 may execute the programcode accessed from the memory elements 304 via a system bus 306. In oneaspect, the data processing system may be implemented as a computer thatis suitable for storing and/or executing program code. It should beappreciated, however, that the data processing system 300 may beimplemented in the form of any system including a processor and a memorythat can perform the functions described within this specification.

The memory elements 304 may include one or more physical memory devicessuch as, for example, local memory 308 and one or more bulk storagedevices 310. The local memory may refer to random access memory or othernon-persistent memory device(s) generally used during actual executionof the program code. A bulk storage device may be implemented as a harddrive or other persistent data storage device. The processing system 300may also include one or more cache memories (not shown) that providetemporary storage of at least some program code in order to reduce thequantity of times program code must be retrieved from the bulk storagedevice 310 during execution. The processing system 300 may also be ableto use memory elements of another processing system, e.g. if theprocessing system 300 is part of a cloud-computing platform.

Input/output (I/O) devices depicted as an input device 312 and an outputdevice 314 optionally can be coupled to the data processing system.Examples of input devices may include, but are not limited to, akeyboard, a pointing device such as a mouse, a microphone (e.g. forvoice and/or speech recognition), or the like. Examples of outputdevices may include, but are not limited to, a monitor or a display,speakers, or the like. Input and/or output devices may be coupled to thedata processing system either directly or through intervening I/Ocontrollers.

In an embodiment, the input and the output devices may be implemented asa combined input/output device (illustrated in FIG. 15 with a dashedline surrounding the input device 312 and the output device 314). Anexample of such a combined device is a touch sensitive display, alsosometimes referred to as a “touch screen display” or simply “touchscreen”. In such an embodiment, input to the device may be provided by amovement of a physical object, such as e.g. a stylus or a finger of auser, on or near the touch screen display.

A network adapter 316 may also be coupled to the data processing systemto enable it to become coupled to other systems, computer systems,remote network devices, and/or remote storage devices throughintervening private or public networks. The network adapter may comprisea data receiver for receiving data that is transmitted by said systems,devices and/or networks to the data processing system 300, and a datatransmitter for transmitting data from the data processing system 300 tosaid systems, devices and/or networks. Modems, cable modems, andEthernet cards are examples of different types of network adapter thatmay be used with the data processing system 300.

As pictured in FIG. 15, the memory elements 304 may store an application318. In various embodiments, the application 318 may be stored in thelocal memory 308, the one or more bulk storage devices 310, or separatefrom the local memory and the bulk storage devices. It should beappreciated that the data processing system 300 may further execute anoperating system (not shown in FIG. 15) that can facilitate execution ofthe application 318. The application 318, being implemented in the formof executable program code, can be executed by the data processingsystem 300, e.g., by the processor 302. Responsive to executing theapplication, the data processing system 300 may be configured to performone or more operations or method steps described herein.

Various embodiments of the invention may be implemented as a programproduct for use with a computer system, where the program(s) of theprogram product define functions of the embodiments (including themethods described herein). In one embodiment, the program(s) can becontained on a variety of non-transitory computer-readable storagemedia, where, as used herein, the expression “non-transitory computerreadable storage media” comprises all computer-readable media, with thesole exception being a transitory, propagating signal. In anotherembodiment, the program(s) can be contained on a variety of transitorycomputer-readable storage media. Illustrative computer-readable storagemedia include, but are not limited to: (i) non-writable storage media(e.g., read-only memory devices within a computer such as CD-ROM disksreadable by a CD-ROM drive, ROM chips or any type of solid-statenon-volatile semiconductor memory) on which information is permanentlystored; and (ii) writable storage media (e.g., flash memory, floppydisks within a diskette drive or hard-disk drive or any type ofsolid-state random-access semiconductor memory) on which alterableinformation is stored. The computer program may be run on the processor302 described herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of embodiments of the present invention has been presentedfor purposes of illustration, but is not intended to be exhaustive orlimited to the implementations in the form disclosed. Many modificationsand variations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the present invention.The embodiments were chosen and described in order to best explain theprinciples and some practical applications of the present invention, andto enable others of ordinary skill in the art to understand the presentinvention for various embodiments with various modifications as aresuited to the particular use contemplated.

1. A system for selecting one or more devices in a wireless network for:transmitting, receiving and/or processing a radio frequency signal forpresence and/or location detection; and performing networkcommunication; wherein said system comprising at least one processorconfigured to: determine a suitability of each of a plurality of devicesfor transmitting, receiving and/or processing a radio frequency signalfor presence and/or location detection while leaving sufficientresources for network communication, wherein said plurality of devicescomprises at least one light device; and wherein network communicationcomprises transmitting network messages of a lighting control system;select a subset of devices from said plurality of devices based on saidsuitability determined for each of said plurality of devices, andinstruct at least one of said subset of devices to act as a device fortransmitting, receiving and/or processing a radio frequency signal forpresence and/or location detection.
 2. A system as claimed in claim 1,wherein said at least one processor is configured to determine at leastpart of said suitability of a device of said plurality of devices byassessing expected and/or past use of a lighting and/or network functionof said device and/or any other expected and/or past use of said device.3. A system as claimed in claim 1, wherein said at least one device usesa first protocol to transmit, receive and/or process said radiofrequency signal and a second protocol to transmit and/or receivenetwork messages.
 4. A system as claimed in claim 1, wherein said atleast one processor is configured to determine at least part of saidsuitability of a device of said plurality of devices by assessing atleast one of: said device's hardware capabilities, said device's one ormore RF characteristics, said device's mounting orientation, wirelessinterference close to said device, and whether said device is operatedby a battery-operated wall switch or a legacy wall switch, an occupancysensor, a motion sensor, a sensor bundle, a window blind controllerand/or a mains-powered wireless switch.
 5. A system as claimed in claim1, wherein said at least one processor is configured to select saidsubset of devices as part of commissioning said plurality of devicesand/or after commissioning said plurality of devices.
 6. A system asclaimed in claim 1, wherein said at least one processor is configured todetermine said suitability of each of said plurality of devices fortransmitting, receiving and/or processing said radio frequency signal bydetermining a suitability of a plurality of groups of said plurality ofdevices for transmitting, receiving and/or processing said radiofrequency signal, each of said plurality of groups comprising at leasttwo of said plurality of devices.
 7. A system as claimed in claim 6,wherein said least one processor is configured to determine whether twoof said plurality of groups have a device in common and target a same oradjacent sensing area and determine one of said two groups not to besuitable in dependence on said determination.
 8. A system as claimed inclaim 1, wherein said least one processor is configured to determinewhether a communication quality between a pair of said plurality ofdevices is below a certain threshold and determine said pair not to besuitable in dependence on said determination.
 9. A system as claimed inclaim 1, wherein said least one processor is configured to determine, ata later moment, a further suitability of each of said plurality ofdevices for transmitting, receiving and/or processing said radiofrequency signal, select a further subset of devices from said pluralityof devices based on said further suitability determined for each of saidplurality of devices, and instruct at least one of said further subsetof devices to act as a device for transmitting, receiving and/orprocessing a radio frequency signal for presence and/or locationdetection.
 10. A system as claimed in claim 1, wherein said at least oneprocessor is configured to determine at least part of said suitabilityof a device of said plurality of devices based on historical datarelating to said device and/or by assessing said device's spatiallocation and/or environmental condition.
 11. A system as claimed inclaim 10, wherein said at least one processor is configured to determinea transmission power and/or directionality for a radio frequency signalto be transmitted by said device based on said device's spatiallocation.
 12. A system as claimed in claim 1, wherein said at least oneprocessor is configured to determine said suitability of each of saidplurality of devices for transmitting, receiving and/or processing saidradio frequency sensing signal for a certain type of detection.
 13. Amethod of selecting one or more devices in a wireless network for:transmitting, receiving and/or processing a radio frequency signal forpresence and/or location detection; and performing networkcommunication; wherein the method comprising: determining, by at leastone processor, a suitability of each of a plurality of devices fortransmitting, receiving and/or processing a radio frequency signal forpresence and/or location detection while leaving sufficient resourcesfor network communication; wherein said plurality of devices comprisesat least one light device; and wherein network communication comprisestransmitting network messages of a lighting control system; selecting,by at least one processor, a subset of devices from said plurality ofdevices based on said suitability determined for each of said pluralityof devices; and instructing, by at least one processor, at least one ofsaid subset of devices to act as a device for transmitting, receivingand/or processing a radio frequency signal for presence and/or locationdetection.
 14. A non-transitory computer readable medium comprising acomputer program product storing at least one software code portion, thesoftware code portion, when run on a computer system, is configured forperform the steps of claim 13.